FIX: migration didn't determine catalog sizes correctly
Merge pull request #337 from reneme/fix_catalog_size_in_migration

FIX: Migration Didn't Determine Catalog Sizes Correctly

This fixes swissknife migrate which was broken by the newly introduced nested catalog size bookkeeping. Additionally it now fills the newly introduced size field in the nested_catalogs table for all migrated nested catalogs on the go.
start development of cvmfs python library
add .cvmfspublished into _common
abstract Repository for addition of 'RemoteRepository'
add a manifest (.cvmfspublished) abstraction class
add remote repository support
adapt global collection functions
FIX: non-available RemoteRepository throws HTTPError
set manifest field 'L' as micro catalog
add REST specific information to _common
replace urllib by requests
add REST specific query methods
read last snapshot timestamp if appropirate
figure out cvmfs binary versions in python
store server version in Repository object
figure out if stratum 1 is currently snapshotting
refactor get rest requests
add a 'start_replication' method in RemoteRepository
minor refactoring in RemoteRepository