Fix moar

FIX: Make CE2CS agent get a fresh copy of the cs data before attempting to modify it. Closes #1151
FIX: Do not attempt to untar directories before having checked if they are tarfiles. Closes #1161
FIX: Do not create useless backups due to slaves connecting and disconnecting. Fixes #959
FIX: CSVs without end date will be generated now. Closes #288
FIX: Take into account invalid values. Closes #949
NEW: Hack added to prevent retrying with 'Insane environment'. Closes #655 
CHANGE: Do not accept VOMS proxies when uploading a proxy to the proxy manager. Updates #353 wrt VOMS
CHANGE: Use cStringIO for ANY read that's longer than 16k (speed improvement) + Less mem when writing data to the net. Improves #953