Feature: cvmfs_swissknife lsrepo Optionally Prints Catalog Size and Entry Count

This (partially) implements the feature request in [CVM-611](https://sft.its.cern.ch/jira/browse/CVM-611). `cvmfs_swissknife lsrepo` now accepts the switches `-s` and `-e` that print both the catalog file sizes (decompressed in bytes) and the contained directory entries.