This PR intends to simplify CLI option processing (mostly the ones related to logging) and remove duplicate options, which will in turn pave way for fixing issue #1018

Note: this branch started as a fix for issue #1018, but got transformed into CLI option rearrangement. Perhaps the last commit should be a separate PR

Public API changes:

1. All options are now specified after commands. That is, if before one would call

    $ nucypher alice --debug init --federated-only
   

   after the PR the syntax would be

    $ nucypher alice init --debug --federated-only
   

   Cons:

   • this goes somewhat against click philosophy (see this click issue).
   • there is some amount of "magic" in config.py required for this to work.

   Pros:

   • this helps avoid code duplication (for option definition and processing).
   • this helps user discover these options in --help. That is, if before, in order to find out about --debug, one would have to call nucypher --help in addition to nucypher alice --help, now just nucypher alice --help will be enough - all the options will be there.

2. Added --no-sentry option to turn off Sentry logging.

3. --debug now just sets/unsets certain otherwise available CLI options (TODO: to be determined which ones exactly), acting as a shortcut.

4. NUCYPHER_SENTRY_LOGS and NUCYPHER_FILE_LOGS have stricter requirements for their contents (whatever strtobool can recognize)

5. TODO: --verbose sets the logging level

6. TODO: add an option to turn off banners

Internal changes:

1. GlobalLogger class manages all logging and observers.

2. TODO: get rid of emit methods in random classes and use standard existing logging facilities?