Added ability to paint in chunk w/ selected block

Also added an experimental INI-only setting to remove flicker.
It's not in the menu because it works by using reflection to set
DoubleBuffered (a protected property) to true from outside the class, so
it might not work in certain situations.
Anti-flicker now works in a more reliable way

More specifically, it now only redraws the part that changed until you
release the mouse button. It also checks array bounds before attempting
to access the array.
Put KensSharp reference paths back to normal.
Merge pull request #2 from flarn2006/master

Added chunk painting feature (2nd pull request)