Add inspector view element for bindings object.

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We want to improv devX by providing an inspector view element to observe the state of the bindings variable used to share state between notebook cells.

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first steps:

• integrate own generic extension (or existing one)
• attempt to display Polyglot variables

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installing Jupyter extensions: https://jupyter-contrib-nbextensions.readthedocs.io/en/latest/install.html

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made first subtle modification to existing variable inspector extension in order to see whether we can use this as a base for our Polyglot inspector

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current state: