Return comment modifiable indicators to client

To keep the logic foucused on the server, return to the client
properties of each comment and property modifiable state
in the context of a user.  The server will still reject unauthorized
edits.
Set the auto-id on new users

This was causing issues in the unit tests because the
db id was not set.
Tests for modifiable indicators on comment info
Merge pull request #14 from azavea/topic/comment-enhance

Comment enhancments for client