Merge pull request #314 from Gama11/dev

FlxParticle / FlxEmitter improvements
fix for issue #318 (Function and Numpad keys caused crashes on cpp target)
little improvement in input classes - they don't use Dynamics and reflection now
Merge pull request #319 from Gama11/dev

FlxTrail bugfixes and changes
Improved error log for invalid keys

- pressed() in FlxInputStates now also calls FlxG.log()
- the Key string is now logged as well, making the error log more
helpful
- the error log also covers the possiblity of the key being invalid
without being a function or number key