#959 GOOGLE_APP_ENGINE should be definable in workspace too

[Aleksander Kowalczyk]

Currently you have to define GOOGLE_APP_ENGINE string substitution as a project's property (PyDev - PYTHONPATH) while this library path commonly depends on developer's environment.
When defined in project, it will be saved in .pydevproject which is intended to be shared between developers. This makes difficult to store this file in version control, as multiple developers require .pydevproject having different paths to GOOGLE_APP_ENGINE stored in the file.

The resolution would be to honour also workspace-level variable (set in Pydev - Python Interpreter - Environment Variables) of the same name.