Defrag and partitionable slots

Best to view the diff without whitespaces:
https://github.com/kreczko/htcondor/compare/HEP-Puppet:master...kreczko:defrag-part-slots?expand=1&w=1
By default Eclipse (Geppetto) removes trailing spaces on save.

With this pull request memory is no longer overcommited for non-partitionable slots.
The default is still the same as before (```partitionable_slots = true```)