ContactInGroup filter only supports IN/NOT IN so map =/!= (if passed in via...

ContactInGroup filter only supports IN/NOT IN so map =/!= (if passed in via API) so the filter still works

This just makes it easier - eg. if you specify "group = 3" (the api3 explorer defaults to "=") then it will work and you don't have to remember to select "IN".

Thanks

merged

mentioned in commit 12b744e1