Localize groups name/description, group sets name

Let's introduce the following translation contexts:
- *GroupName* for group names
- *GroupDescription* for group descriptions
- *GroupSetName* for group set names

Whan using with models, you can use the following methods:
- Group::getGroupDisplayName
- Group::getGroupDisplayDescription
- GroupSet::getGroupSetDisplayName
Merge pull request #1485 from mlocati/localize-group-names-v2

Localize groups name/description, group sets name