Added unit tests for unban and isbanned

Simple unit tests for Unban to handle
- Missing username
- Non-Admin use of command
- Unban nonexistent user
- Cannot Unban another Admin
- Cannot Unban yourself
- Unbanning a banned user

for IsBanned to handle
- Get banned user list
- Non-admin user
- Non-existent user

Updated test when trying to ban yourself to appropriate exception text

Updated LanguageResources message for Unban_UserRequired