Include ground kernel app only if we have PCL

For now, the ground filter can't run without PCL, so we should ghost it
away if we don't have PCL.
Merge pull request #464 from gadomski/ground-depends-on-pcl

Include ground kernel app only if we have PCL
Factor out rxp moving average to a free function

This makes it easier to test.
Always test WITH_STUBS=OFF

More useful than WITH_STUBS=ON, since our out-of-the-box builds are no
stubs.
Merge pull request #465 from gadomski/test-without-stubs

Always test WITH_STUBS=OFF
add PCL version to full version string (if present)