moved logging functionality up to groupsAndMembers
Merge pull request #455 from leider/master

Refactored: moved logging functionality up to groupsAndMembers
saving objects now uses update instead of remove-insert

external behavior is the same internally exceptions occurring between the two calls (remove/insert) now simply cannot happen anymore.
Merge pull request #456 from leider/master

saving objects now uses update instead of remove-insert
Invalidate the sympa cache when a user subscribes or unsubscribes to/from a list.