Issue #37 and Issue #28

adding support for specifying groups for appservers and forests
I'm not doing anything to remove hosts before deleting the group. My guess is that this will fail. I also figure that people probably don't want to really remove groups from Roxy anyway. I added another ticket #288 for warning against wiping against PROD to discourage such activity. The implementation I have here is sufficient for keeping the self-test from gumming up the works with leftover groups, but not good enough for real clustered environments. I'm going to leave it for now and wait to see if anyone requests the ability to add/remove hosts to/from groups.