Display Spyder's or Jupyter's context menu on right click

[jitseniesen]

This is a follow-up from PR #396. In version 0.4, right clicking brings up Spyder's context menu (with New, Open, Save). After #396, something has changed and right-clicking brings up Jupyter's context menu.

I am not yet sure what to do about this. All actions in Spyder's context menu can also be performed via the hamburger menu, so we don't lose functionality by displaying Jupyter's context menu. Furthermore, Jupyter's context menu does have some useful stuff in it.

[jitseniesen]

I checked and actually, in version 0.4 of the plugin a right-click does display Spyder's context menu. However, at least on my system the menu does not have the "New notebook" and "Open notebook" menu items to which the text on the welcome screen refers, as shown below. This may be a regression between versions 0.3 and 0.4 (or I am not remembering it correctly).

Shift+right-click shows the Qt context menu, as shown below. This was added in PR #349 because the Qt context menu has an item for saving plots.

After PR #396, right-click shows the Jupyter context menu instead of the menu with "Zoom in" and "Zoom out":

Shift+right-click shows the same Qt context menu as before.

[ccordoba12]

However, at least on my system the menu does not have the "New notebook" and "Open notebook" menu items to which the text on the welcome screen refers, as shown below

This is perhaps a regression when the plugin was migrated to the new API. I think we should address that along with increasing the dependency on Spyder (>=5.4.3 once it's released) to fix issue #386, and release 0.4.1 with those fixes.

After PR #396, right-click shows the Jupyter context menu instead of the menu with "Zoom in" and "Zoom out"

I think we should keep that menu to maintain consistency with Jupyter notebook. In that way, users that move from regular Jupyter notebook to the Spyder one would encounter the same experience.

[jitseniesen]

We decided to stick with the Jupyter context menu, so nothing needs to be done here.