multiple Traverse() calls for one CatalogTraversal object
pre-define root catalog hashs in T_CatalogTraversal
TEST: verify multi traversal feature of CatalogTraversal<>
Merge pull request #491 from reneme/feature-multi_clg_traversal

Feature: CatalogTraversal<> Objects can be Reused with Multiple Entry Points

The CatalogTraversal<> template can now be reused for multiple traversal operations. This will become handy, when it is used for the garbage collection of a repository with multiple tags. Hence each tag will be an entry point into the repository to be garbage collected.

Additionally this contains an adaption/extension of the respective test suite.