GitHub: migrate away from Subversion repository

Migrate away from Subversion repository.  Remove temporary
.idea/.gitkeep file.  This file was only necessary when manually
importing the last few commits from Subversion.  Update IntelliJ
configuration to recognize local working copy as Git instead of
Subversion.  Add initial .gitignore to keep build droppings out
of the Git repository.  Fix the SVN source control test to no longer
rely on the fact that CruiseControl itself uses Subversion.

Signed-off-by: Kent R. Spillner <kspillner@acm.org>