Small UI improvements and minor bug fixes

## GUI
- The tooltip GUI object now functions properly and can be applied to any control automagically.
- You can now click on a slider to move the value to that point rather than having to drag it there.

## Admin menu:
- It is now possible to define tooltips for admin menu command buttons.
- A lot of buttons in the admin menu now have tooltips to help explain what they do.

## Minor errors:
- Fixed nil values in "InheritsFrom" arrays causing an error.
- Fixed an error in the logging plugin if the commander logging in was nil.

## Map vote:
- You can now weight the chance of a map being chosen for the map vote so that each map no longer has equal chance. The default is still equal chance.

## Cleanup/misc
- Moved the base plugin metatable to its own file.
- Cleaned up the chatbox code.
- Made the MotD use the existing title bar code rather than doing it in its own special way.
- Slightly improved the map object's iteration performance.