Implement (interpreted) ALE as a GEMOC xDSL

If ALE was implemented as a GEMOC DSL, it would be a pefect "eat your own dog food" use case: this would make us use the GEMOC Studio to implement a language that we would actually use (to implement other DSLs).

In particular, all GEMOC generic runtime services (omnsicient debugging / trace management) would be available for ALE, giving us a great incentive to enhance the usability of the GEMOC debugger, which would become the official ALE debugger.