## Summary

This PR wraps up the remaining `Detection Engine` meta tickets: elastic#55585, elastic#54935, and elastic/siem-team#498
- [x] Histogram bar interval (bar counts and widths) consistency (elastic#55585)
  - [x] Make the bar intervals a consistent 32 bars across the board
  * Enabled `extended_bounds`, `min_doc_count: 0`, and now setting consistent `fixed_interval` when querying to ensure the entire daterange is displayed across all histograms.
- [x] Filter out the "untitled" timelines from both timeline selection options during rule creation (elastic/siem-team#498)
  - [ ] ~Import query from saved timeline~
    * For 7.7 tracking ticket here: elastic#56079
  - [x] `Investigate detections using this timeline template` 
- [x] Everywhere we use "Alerts" (Overview page, Host Tab, Network Tab) we should change the term to "External Alerts"
  - [x] Updated Host Page Tab/Table/Histogram/Breadcrumbs
  - [x] Updated Network Page Tab/Table/Histogram/Breadcrumbs
- [x] Updated DE permission/index  error doc links to go to [corresponding DE docs section](https://www.elastic.co/guide/en/siem/guide/7.6/detection-engine-overview.html#detections-permissions)
- [x] Removed `frequency` in favor of `count` for remaining histograms

##### Inconsistent Histogram intervals
![image](https://user-images.githubusercontent.com/2946766/73161560-04a82300-40a9-11ea-950f-ea56f9a5bfd7.png)


##### Consistent Histogram Intervals
![image](https://user-images.githubusercontent.com/2946766/73159564-fefc0e80-40a3-11ea-9b9d-4d15899dabd2.png)


cc @MichaelMarcialis @cwurm @MikePaquette 

### Checklist

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- [ ] ~This was checked for cross-browser compatibility, [including a check against IE11](https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md#cross-browser-compatibility)~
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