AADL Navigator: Double-click on instance model content doesn't open editor

[AaronGreenhouse]

Double clicking on the instance model content in the AADL Navigator doesn't link to the editor.

[AaronGreenhouse]

Created new branch for this: 1572_aadl_navigator_intance_model_doublelick

[AaronGreenhouse]

Started trying to fix this, but it doesn't work reliably.

Was having problems with eResource() sometimes returning null in the new openEditorToElement(). That is, the InstanceObject being selected sometimes doens't have the eResource set. But then sometimes it magically comes back, and then disappears again.