Dw erldb ets mnesia

Major change to erldb:

- Adding mnesia worker, still need work, close #22 
- Adding ets worker, still need work close #21 
- Added tests for mnesia and ets worker
- Changed erldb to work with workers
- Changed how erldb_init works close #33 
- Added script to compile models
- Changed erlang.mk now takes model as compiling option for compiling models
- Changed so that model_path can be set in erldb.app.src env