Add a way to localize hardcoded strings in GUI
A current idea is to use YAML files used by Lua scripts. It is an obvious choice because OpenMW's UI later is supposed to be dehardcoded by Lua scripts, to translation files will be reusable.
We can use a #{contextName:keyName}
syntax to tell MyGUI to read from YAML, while using a current #{keyName}
syntax to read GMSTs. Later there can be introduced a some kind of alias system which will allow L10nManager to read GMSTs "under the hood" when it would make sense.