Implement copybutton for the shell session

[serhiy-storchaka]

Currently the Python session code blocks has a button on top-right corner which hides the >>> and ... prompts and the output.

Would be nice to implement similar button for the shell session code blocks. It should hide the $ prompt and the output.

[terryjreedy]

This tutorrial example has one of each. But the command session has only one $ prompt and command. Are there other examples with more?

[freddrake]

That example only shows the Python prompt as output; there's no issue of there being additional input there. (I haven't looked for other examples.)

That example also mistakenly colorizes the first > of the Python prompt as a shell continuation prompt.

[pradyunsg]

This exists in the form of a Sphinx extension now: https://github.com/executablebooks/sphinx-copybutton

[hugovk]

Please see PR #295.