Epsilon tool service XMI support

[barnettwilliam]

The Epsilon micronaut tool services should support XMI model as inputs so language workbench outputs can be used in activities.

[barnettwilliam]

@szschaler while trying to test the modified micronaut service, there is a difference between what platform type conversion expects when the type is a model.

The to-xmi function that's generated by the Xtext build doesn't take a metamodel as an input, presumably it already has this, but because the target type is model the platform expects the conversion function to have a corresponding metamodel. The platform fails to find a matching conversion function as the required metamodel is missing.

We could either:

1. Create an exception in the type conversion for all *-generated types so that a metamodel is not required for the model conversion.
2. Add a metamodel as an input parameter of to the xtext to-xmi function, the tool function doesn't necessarily need to use it

[szschaler]

I would go with the second option.

[barnettwilliam]

XMI Epsilon support in PR epsilonlabs/playground-micronaut#1

Suggested change in PR mdenet/platformtools#57, only required configuration file update.