ContextMenuTool not advertised in any api module

[notmatthancock]

This is a useful tool, but not easily discoverable. Perhaps it can go in enable.tools.api?

[kitchoi]

While we are at this, it might be worth moving the content of the module out of the enable.tools.pyface namespace (which contains only one thing)? We can keep the imports as aliases for backward compatibility.

Looking into the pull request that added the tool (#84), looks like the original intent was to keep pyface an optional dependency. But I think the package has changed since and enable.tools.api probably already requires pyface one way or another (e.g. hover_tool imports pyface).

[kitchoi]

I think I should open a separate issue for the subpackage, it is orthogonal to exposing the tool via the api module. Sorry for noise.

[corranwebster]

Yes, this was written when Enaml was more of a thing and it was annoying to have Pyface as a dependency when writing Enaml apps, so we were working to remove it. There's also some gorpiness around the Pyglet/OpenGL and VTK/TVTK backends because we don't have a Pyglet or TVTK backend for Pyface.

We have to be a bit careful - I think it is OK for us to have the Wx or Qt backends depending on Pyface as a matter pr practicality, but making this part of the public API may break the Pyglet backend, for example.