Updated controls and code

* Added keyboard speed keys:
** LCTRL: decrease speed by factor of 0.9
** TAB: increase speed by factor of 1.1
** LSHIFT: temporarily (while held) increase speed by factor of 100.0
* Improved code:
** modularized planetary shading into it's own effect
** displacement, sky, space shaders are subclasses
** .fx files include the new PlanetHelper.fx which has the helper
functions and constants.