Add article and example on processing Ecore metamodels with Epsilon

[kolovos]

It would be useful to have a short article explaining that Ecore/Emfatic metamodels are EMF models too and therefore they can be queried, validated etc. like any other EMF model in Epsilon. We should also include some instructions on using the EPackage Registry view to explore Ecore itself + links to external documentation about Ecore.

[kolovos]

We now have a minimal example that shows how to query Ecore metamodels with EOL.

[alfonsodelavega]

There is also a Pinset example that shows how to calculate basic metrics for the EClasses of a metamodel. This one is executed via an Eclipse run configuration (also included).