PowerSet() added to mapset API.
PowerSet() added to mapset API. -r1
fixed screwed up untabified files.
removed deferred set.RUnlock() in PowerSet() reflecting the performance issues fixed in commit 59f4d6361416fb1ae4e84d6b09d300b6895d74ff.
Merge pull request #18 from ashkang/master

Added PowerSet() for generating all subsets of a given set