Add a way to read, display and manage the environment variables passed to the IPython console

[ccordoba12]

This is needed to make Spyder work correctly with Tensorflow without starting it from a terminal. For example see:

http://stackoverflow.com/questions/41344017/why-does-the-tensorflow-module-import-fail-in-spyder-and-not-in-jupyter-notebo

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@andfoy, this is for 3.2, so please don't worry about it right now. I opened this issue so we don't forget to address it in the future ;-)

[ccordoba12]

This new entry should be added to our project preferences too.

[goanpeca]

Whats the idea here? to have a standalone pop up widget/dialog for this (a 2 column QTableView) or embed this inside the preferences... or both or?

[ccordoba12]

We could have both, I still haven't decided it. In any case, we already have an env vars viewer (in the Options menu of the Python console), we just need to populate it at startup.