Allow to keep the build dir after succesful build

Set the option cleanupbuild to False to keep the build dir after a
succesful build. Can be helpfull for debugging purposes.
Merge branch 'develop' into cleanupbuild

Conflicts:
	easybuild/framework/easyconfig/default.py
Merge pull request #11 from boegel/cleanupbuild

sync with develop
fix conflict resolution fail
replace 'cleanupbuild' easyconfig parameter by '--cleanup-builddir' command line option, and enhance unit tests
Merge pull request #12 from boegel/cleanupbuild

replace 'cleanupbuild' easyconfig parameter by '--cleanup-builddir' command line option, and enhance unit tests
Cleanupbuilddir: make help message correcter
Merge pull request #853 from wpoely86/cleanupbuild

Allow to keep the build dir after succesful build