Feature: Integrate `cvmfs_swissknife dirtab` into `cvmfs_server`

This integrates the `.cvmfsdirtab` processing of `cvmfs_swissknife` into `cvmfs_server`. Additionally it slightly adapts the integration test case 544 to check for one more warning message. However, currently the `.cvmfsdirtab` implementation *does not* support relative negative rules. This will come in a later pull request.

**Note:** This contains the Pull Requests [Feature: Pathspec classes](https://github.com/cvmfs/cvmfs/pull/448), [Feature: Dirtab Wrapper Class](https://github.com/cvmfs/cvmfs/pull/449), [Feature: Simple Catalog Manager](https://github.com/cvmfs/cvmfs/pull/450) and [Feature: cvmfs_swissknife dirtab](https://github.com/cvmfs/cvmfs/pull/451).