Add recursive_group_search_fallback option

This lets us disable the fallback recursive group search when
virtual attributes aren't enabled. This may be necessary for large
directories that don't support virtual attributes due to performance
issues.
Avoid recursive group search when not enabled
Fix for change in group_filter signature
Merge pull request #31 from github/recursive-group-search-fallback-disable-option

Add recursive_group_search_fallback option