Add AI interface

A problem remains(how to judge a new block)
Merge from master
Finish AI

FIx a bug in game(clear bar)
multiple thread AI

And add variable in SquareArray
Fix bugs
Merge branch 'master' of https://github.com/xvblack/Tetris-se2013

Conflicts:
	Tetris/Block.cs
Fix the bug of clearbar

because of merge
Basic GUI finish
Basic Dual Game GUI finish

And reduce the drawing times
Fix a bug
Merge remote-tracking branch 'origin/BasicGUI' into gamelogic

Conflicts:
	Tetris/TetrisGame.cs
Merge FIx