Internationnalization: buggles etc.

Coded in the i18n.tr calls.
Put the base support as much as possible into the abstract classes. the
derived classes only having to add registration code and language
selection handling (see World, BuggleWorld and
EntityControlPanel/BuggleButtonControlPanel).
Todo: build the .pot/.po files
Merge pull request #96 from fstengel/Test

Internationnalization: buggles etc.
save a very good link on scala scripting (and delete from TODO a useless cosmetic that'd be hard to implement)
Entities cannot have their own org.xnap.commons.i18n.I18n, use the static Game.i18n instead