bosh commands now run in cf_release_branch_dir [fixes #99]

cf_release_dir now holds the various branch clones
of cf-release; so cf_release_branch_dir is the directory
to the clone being used for the current command
inception VM git does not have --no-recurse-submodules flag
use cf-release <branch> instead of master when cloning

Otherwise was always defaulting to master on clone;
then getting conflicts with <branch> when pulling
later.