add initial implementation of Dirtab
TEST: unit test for initial Dirtab implementation
positive rules in dirtab must be absolute
TEST: unit test for absolute positive rules
split Dirtab::IsMatching() into IsMatching() and IsOpposing()
add Dirtab-accessors for rule categories
TEST: unit test for Dirtab::IsOpposing()
add scaffold for swissknife command 'dirtab'
dirtab processing in cvmfs_swissknife
print warning for useless dirtab rules
FIX: skewed access rights of .cvmfscatalog
FIX: recreate manually deleted .cvmfscatalog
replace dirtab processing in cvmfs_server
FIX: dirtab processing needs scratch dir
TEST: adapt integration test case 544