add prerelease script generator
prerelease: allow unreleased packages in underlay, create output folder on-demand, print execution instructions
ensure uid is not zero
code style
improve check for empty folder but prerelease scripts
improve error message when catkin_test_results is unavailable
change cmi_and_test to invoke the targets 'all', 'tests' and 'run_tests' separately
Merge pull request #24 from dirk-thomas/master

add prerelease script generator