By moving this code and associated utility methods into Application we
nearly complete the long-in-progress refactoring of the monolithic
kdesrc-build script into proper classes/objects.

The kdesrc-build script itself is nearly bare, but there's still a bit
more to do.

At least it should be easier to make individual test scripts to test
different bugs instead of having a monstrosity of a kdesrc-build-test
script that has to maintain a common state.

I've tested this in each way that I'm able (run needing to make a new
source dir, build dir, new install and log dir, run updating existing
checkouts, bzr/svn/git/kde-projects all tested, etc.). But this was a
large move so let me know if I've missed anything.