sagemathgh-36962: Add is_(sparse_)paving() and automorphism_group()
    
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->
Added three functions to the main matroid class.

<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->
These correspond to two connectivity check algorithms, `is_paving()` and
`is_sparse_paving()`, and a miscellaneous function
`automorphism_group()`. These are all standard and regularly used
notions in matroid theory.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [x] I have created tests covering the changes.
- [x] I have updated the documentation accordingly.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on
- sagemath#12345: short description why this is a dependency
- sagemath#34567: ...
-->

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#36962
Reported by: gmou3
Reviewer(s): Travis Scrimshaw

sagemathgh-36962: Add is_(sparse_)paving() and automorphism_group()
    
<!-- ^^^^^
Please provide a concise, informative and self-explanatory title.
Don't put issue numbers in there, do this in the PR body below.
For example, instead of "Fixes sagemath#1234" use "Introduce new method to
calculate 1+1"
-->
<!-- Describe your changes here in detail -->
Added three functions to the main matroid class.

<!-- Why is this change required? What problem does it solve? -->
<!-- If this PR resolves an open issue, please link to it here. For
example "Fixes sagemath#12345". -->
<!-- If your change requires a documentation PR, please link it
appropriately. -->
These correspond to two connectivity check algorithms, `is_paving()` and
`is_sparse_paving()`, and a miscellaneous function
`automorphism_group()`. These are all standard and regularly used
notions in matroid theory.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->
<!-- If your change requires a documentation PR, please link it
appropriately -->
<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
<!-- Feel free to remove irrelevant items. -->

- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [x] I have created tests covering the changes.
- [x] I have updated the documentation accordingly.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on
- sagemath#12345: short description why this is a dependency
- sagemath#34567: ...
-->

<!-- If you're unsure about any of these, don't hesitate to ask. We're
here to help! -->
    
URL: sagemath#36962
Reported by: gmou3
Reviewer(s): Travis Scrimshaw

sagemathgh-39382: Correct method `is_sparse_paving`
    
It was brought to my attention that the method `is_sparse_paving` is
incorrect. See
sagemath#36962 (comment).

The method should only check the symmetric differences of `r`-element
circuits rather than all (`r`- and `r+1`-element) circuits.

The algorithm used is based on a somewhat unusual definition which can
be found in https://arxiv.org/pdf/math/0404200.
    
URL: sagemath#39382
Reported by: gmou3
Reviewer(s): Travis Scrimshaw

sagemathgh-39382: Correct method `is_sparse_paving`
    
It was brought to my attention that the method `is_sparse_paving` is
incorrect. See
sagemath#36962 (comment).

The method should only check the symmetric differences of `r`-element
circuits rather than all (`r`- and `r+1`-element) circuits.

The algorithm used is based on a somewhat unusual definition which can
be found in https://arxiv.org/pdf/math/0404200.
    
URL: sagemath#39382
Reported by: gmou3
Reviewer(s): Travis Scrimshaw

sagemathgh-39382: Correct method `is_sparse_paving`
    
It was brought to my attention that the method `is_sparse_paving` is
incorrect. See
sagemath#36962 (comment).

The method should only check the symmetric differences of `r`-element
circuits rather than all (`r`- and `r+1`-element) circuits.

The algorithm used is based on a somewhat unusual definition which can
be found in https://arxiv.org/pdf/math/0404200.
    
URL: sagemath#39382
Reported by: gmou3
Reviewer(s): Travis Scrimshaw

sagemathgh-39382: Correct method `is_sparse_paving`
    
It was brought to my attention that the method `is_sparse_paving` is
incorrect. See
sagemath#36962 (comment).

The method should only check the symmetric differences of `r`-element
circuits rather than all (`r`- and `r+1`-element) circuits.

The algorithm used is based on a somewhat unusual definition which can
be found in https://arxiv.org/pdf/math/0404200.
    
URL: sagemath#39382
Reported by: gmou3
Reviewer(s): Travis Scrimshaw