specify target properties separately from model

[yanntm]

we would like to have a (property file + model) passed to Check call.

When a foreign formalism is used, we want to keep the property file across runs.

Options
a) we have a foreign property file, e.g. .q file for XTA, transform it as well
b) the user writes the props for the GAL target, hopefully the (re)generated model still fits it.We want to keep that file and reuse for subsequent runs.

This feature would ideally involve patching current issues with import mechanism across files, which is broken since Xtext 2.9 for us.