Console improvements

• Unused console backgrounds no longer take up memory
• Input cursor can now move left and right
• Support for selections (Shift-arrow keys, CTRL-A, etc)
• Clipboard support (CTRL-C to copy, CTRL-V to paste, CTRL-X to cut)
• Fixed handling of simultaneous modifier key presses

https://dl.dropboxusercontent.com/u/3518218/21/console.gif

None of this affects chat yet, that's not part of the console. I'll look at it later.