Added basic framework for allowing for ban durations and banning admin.

Added BanningUser, Date(of ban), and Expiration to the db
On join, Expiration is checked, if ban is expired we remove it and the user is allowed on.
When running the ban command, your UAN is used as the banning user, and the date is that moment, with no expiration.
#531
Merge branch 'general-devel' of github.com:TShock/TShock into general-devel
Apparently this file didnt want to be commited last time.
Removed redundant code.
Merge pull request #532 from Olink/general-devel

Ban system is more robust; supports expirations