List of all changes:

- Fixed font issue, that was related to useless "Sparrow" format and
the, also useless FontBuilder. Now fonts have to be created with
AngelCode BMFont utility which can be run through Wine in linux, or
natively in Windows.

- Removed FontDescription class and moved it's data to BitmapFont class

- Implemented stacking of components with GUI,and created a test for it
(StackingTest.java)

- Removed FlyCamera dependency on input, as it is global variable of
Engine 

- Started implementing GUI events handling