FIX: seen but not traversed catalogs are also visited
first push references, than notify listeners
Refactor: DoTraverse()
add traversal strategy parameter
implement depth first traversal strategy
revise documentation of CatalogTraversal<>
FIX: job.postponed for no_close_
FIX: unlink() only if necessary
TEST: T_CatalogTraversal.DepthFirstSearchFullHistoryTraversalNoRepeat
TEST: two more tests for depth first traversal
TEST: depth first traversal sequence
catalog skipping happens in main loop
FIX: DepthFirstTraversal
documentation updates
TEST: update test cases
TEST: scaffold for garbage collector test case
add a simple implementation of a HashFilter
TEST: basic test case for SimpleHashFilter
remove copy and paste garbage
add implementation of GarbageDetector