Make version-gen executable.

For the Makefile that will come in the next commit.
Support using make to build KAE.

It's in my fingers :)
Ignore OnInputLocksModified when not in an editor.

This prevents the NRE on switch to the flight scene and thus breakage of
the vessel initialization sequence.
Add GetAssemblyVersionString() to SystemUtils.

This will retrieve the most informative version string available in the
given assembly: AssemblyInformationalVersionAttrib when available,
otherwise Assembl. AssemblyInformationalVersionAttrib is useful for fancy
version strings (eg, 4.1.2.30-6257-dirty).
Merge pull request #2 from taniwha-qf/version-string

Version string