User delete flag

## User Delete Flag

* Added API method `setDeleteFlag` that will respond to `POST` or `PUT` HTTP methods (`POST` being used for setting the flag, `PUT` being used for resetting it to an empty string).
* Added 5 test cases to the test suite to handle majority of scenarios - need to add more for complete coverage of `setDeleteFlag` 

Open for revisions before it is ready for a merge - to be honest, it probably needs them...

@kentquirk 
Issue reference: #12 
This comment seems to indicate that we must be a server in order to set the delete flag, but the else statement below seems to be allowing the user to set their own delete flag.

One of these is out of sync...  I think I'm prone to believing the comment and not allowing a user's token to delete themselves, but I haven't necessarily thought it through.