First commit of the model generator.

It's unstable and ugly, but it can generate some classes based on some
jsons. (Twitter, for example.)

Know bugs:

You must have a project selected in order to generate stuff. Otherwise
it won't write anything.
Package name in generated classes is fixed for now.
Fixed selection problem.

Now it will generate the files in the seletected folder/project/package.
If nothing is selected,  you must specify where the files should be
written.