* added addUserGroup and removeUserGroup to the data source interface for users
* added some comments
* changed many double quotes |"| to single quotes |'| where double quotes were not needed
* implemented the remaining methods for the MySQL implementation of the user data source
* added a mode flag to user fields (idea from MattyT) so that fields can be disabled, hidden, etc
git-svn-id: svn://10.0.0.236/trunk@96152 18797224-902f-48f8-a5cc-f745e15eee43