Added icon set
Added doc target. Fixed zip and tar.gz targets
Now using icons. Introduced the concept of glue.

I can now test the plugin easily from with the Unity editor. This is
achieved by factoring out functionality that uses the KSP assembly into
a separate class (called GameGlue.cs). There is a new interface (IGlue)
that contains the glue code.
Added support of Blizzy78 toolbar