Fix JSON output when crashing, and fix help and version information.
Fix JSON output when crashing, and fix help and version information.

When using `--json`, if the command raises an unexpected exception, we
end up showing an empty "success" payload. This is clearly not what we
want. This change insteads records an "Internal Error"  with the
exception's error message, allowing tools to know that something went
wrong.

The help string for `--json` has also been updated to include a trailing
period, matching other help strings. It also now includes an `added_in`
version for the documentation, and the `Version Added` for `JSONOutput`
now correctly shows 3.0.

Testing Done:
Tested `--json` with an exception raised, and saw the exception details.

Saw the corrected help text.

Reviewed at https://reviews.reviewboard.org/r/12163/

reviewboard/rbtools,reviewboard/rbtools,reviewboard/rbtools