Annex registry should have standalone mode

[lwrage]

Currently the annex registry relies on the eclipse extension mechanism. to run in standalone mode there needs to be a registry that can be configured programmatically. This is similar to what EMF does for standalone operation.
child of #1538

[lwrage]

Also, we should add the AADL name of an annex to the registry (or establish the convention that the file extension must match the AADL name).

[AaronGreenhouse]

Found this: https://zarnekow.blogspot.com/2010/06/how-to-deploy-xtext-standalone.html