simple pooling class and FlxTimer recycling

usage example: FlxTimer.getTimer().start(1, timerCallback);
FlxPool putUnsafe() for inner purposes
a little bit better FlxTimer recycling
don't add FlxTimer twice
Fixes a missing class error I was getting after recent updates.

/usr/lib/haxe/lib/flixel/git/flixel/plugin/TimerManager.hx:16: characters 9-37 : Class not found : FlxPool
Merge pull request #546 from timtait/missing-import

Fixes a missing class error I was getting after recent updates.
forgot to null _pool
Stupid error with TimerManager clear() method
Merge pull request #544 from Gama11/dev

Keyboard input refactor
making FlxTimer constructor private (for better recycling)

so the only way to get the new FlxTimer object is to call:
FlxTimer.getTimer();
renaming FlxTimer.getTimer() to just FlxTimer.get() and adding default args.

sorry for spamming
removed unnecessary doc line in FlxTimer
FlxTimer improvement and fix of TimerManager.remove() by @crazysam
Move FlxG.game.prefsSave to FlxG.save, instantiate front ends right away
Further FlxTimer improvements
Make some vars in FlxG and FlxSpriteUtil read-only
Remove FlxG.supportsTouchEvents as it's not used anywhere
More improvements to FlxTimer: added recycle() function, cached manager for faster access.
Fix issue with FlxTimers never triggering callbacks. Added userData variable so users can store and access custom data in FlxTimer callbacks.
Inline optimizations for FlxPool.