MODE-1747 Changed default configuration for workspace caches

Changed the default (built-in) configuration for a repository's in-memory workspace caches (on top of the Infinispan cache used for content) to better work with Infinispan 5.2.

The default can always be overridden in a repository's JSON configuration file.
MODE-1741 - Updated Git connector so that only tree/master content is indexable.
MODE-1741 - Updated the Git connector so that indexable branches are configurable