Initial support for Groups

Create separate object for Users and Groups (using same base class)
Check for uniqueness before adding new users and groups
Remove user_container from everything but add operations
Abstract out a number of functions that are common across users and groups
Make sure all strings passed in to be in a filter are checked
Add new error message: No modifications specified

ipa-admintools/ipa-adduser

@@ -88,6 +88,9 @@ def main():
     except xmlrpclib.ProtocolError, e:
         print "Unable to connect to IPA server: %s" % (e.errmsg)
         return 1
+    except ipa.ipaerror.IPAError, e:
+        print "%s" % (e.message)
+        return 1
 
     return 0