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 
To my read, I believe that if a user token is used and it is requesting a deletion of the current user, then it will allow it.  Where, I took "requires server token" to mean that even if it is the user's own token, they cannot delete their own account.

I was expecting a return() of some sort in the else clause below this, but perhaps that check is being done elsewhere?