allow for legacy read out of catalog counters
INSERT OR REPLACE INTO to write statistics counters back into database
FIX: use FetchRow() instead of Execute() to get data out of the database
generate new statistics counters from 2.1.7 catalog
do not rely on data->new_catalog in 2.1.7 migration
check that PendingCatalog has NO new_catalog in migration from 2.1.7
FIX: count actual chunks not chunked_files
bump catalog schema version + update compatibility checks
use legacy catalog counter loading if catalog versions do not match
integrate catalog migration utility into cvmfs_server
FIX: recursive statistics counters handling and catalog updates
FIX: typo
Merge pull request #190 from reneme/migrate_2_1_7

Migration of 2.1.7 catalogs to 2.1.12