reinstate multiple inheritance and unpacking of source files (required for patching); copy unpacked sources to install dir via os.listdir and os.path.sidir

fix PackedBinary, make sure finalpath is set for all sources (via EB_Binary), get rid of multiple inheritance

remove custom make_install from EB_Binary, no longer needed now copytree isn't used anymore; fix copying from all unpacked directories in EB_PackedBinary

Conflicts:
	easybuild/tools/toolkit.py