Party members order

This feature adds a select input in `Social → Party → Members`, to allow users to sort the party members by level, random, number of pets, or party date joined (the current sorting).

Need to review the design, maybe the select isn't in the right place.

Also note that I couldn't add the **partyOrderChoices** dictionary in `HeaderCtrl` (something about $scope.party.members raising an error at that moment).

Finally, the develop branch needs to be fixed before this feature gets merged: several things seems to have broken (cannot create new user, level him and hatch pets for example, or #1895). When develop is stable again, I'll do more tests and add [additional ordering](https://trello.com/c/yOCLuVng/325-party-members-list-order)