HOTFIX: renaming misnamed 'total_logins' to 'count'

This can't be done after publishing a model, but "total_logins" of UserLogSummary is misnamed--UserLogSummary can refer generically to any type, so "total_logins" is better named "count", and interpreted by the activity_type field.

Testing:
* Did a "grep" on total_logins to confirm all were replaced (Except in the original migrations file)
* Started the server with UserLogs enabled (and disabled) to confirm no exceptions.

Note: also tweaked a report, to limit activity_type to "login".  Tested that the report still works properly.