Allow using context-specific user-defined colors for status bar icon

Hi guys,

This is an experimental extension to ControlPlane that allows to change the color of the status bar icon depending on the active context. That is, the user can pick a color for the status bar icon for a context and when that context is selected according to the rules, the status bar icon color will change accordingly. I think this can be of specific interest to those CP users who prefer icon-only mode for status bar, but would still love to have a simple way to see (from the app icon) which context is active at the moment.

I like it and hope it will be embraced by other people as well. Anyways, let me know if you like it too. Or find it useless. Or have some specific objections to using non-black icon for CP, or using icon color for this specific purpose.

To highlight: I will need help from non-English speakers to properly localize the context edit panel for their specific languages.

Once again, I would like to ask all team members who are able and are willing to build from sources ahead of official releases, to try this extension themselves and share some feedback on it.

P.S. The code changes also include some clean-up and re-factoring to the code, as usual. This time, those are mostly in **ContextsDataSource**.