built new system for handling group content types, in accordance with og-5.x-7.x and upwards. system has been debugged and, unlike the previous system, actually appears to work.

trying to resolve the problem in #253816; changed the unset return value of variable_get() in circumstances where no groups have been set. It's a band-aid, however, as this problem shouldn't be happening in the first place...

small changes to the text for the display layout settings editor buttons. also added t() to the $_POST['op'] value comparisons