Add enhanced version of the XMI deserialization
Add enhanced version of the XMI deserialization

This XMI import now resolves the ereferences. The model 'go-accross'
is not performed in a O(n) style at the moment, but the complexity
should be lower than O(n2). This prototype is a step forward, but the
solution, obviously, requires more work.

pyecore/pyecore,aranega/pyecore