classpath: added jboss modules for the model loader for ceylon/ceylon-compiler#1052
model loader: adapted to latest model loader API for ceylon/ceylon-compiler#1052

Required to support multiple modules of the same name different version at runtime, but
not tested yet.
language-module.txt: updated for filename casing blunder
Metamodel: updated the API for the recent model loader changes in ceylon/ceylon-compiler#1052