Added getCurrentGameParams and fixed a few minor bugs.

* Added ability to get the current GameParams. 
* Fixed fullscreen/windowed mode support.
* Fixed cursor visibility. Default to be visible is not given in fullscreen. Now always set correctly.
* Added variables for window title and mode. Also added variable for cursor visibility. Added them so one can ask for their values with getCurrentGameParams.
* Added Show instance for GameParam.

Would be happy to see these changes in the next version.