Hide actions when they're not available in orb-note-actions

[zaeph]

It might be better to hide the actions which are not available with the current file when running orb-note-actions.

For instance, if a file does not have a PDF, it should probably not show you the option. Another option might be to change the completion-string for that action to something that indicates that a PDF is not present.

[j-steinbach]

I believe that from a user-design perspective, the unavailable options should be "greyed out" out.

Otherwise there is the danger that new/unexperienced users will not know that there is something missing and will never take steps to "fix" the issue.

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Damn, Github issues are a great way to procrastinate..

[myshevchuk]

I believe that from a user-design perspective, the unavailable options should be "greyed out" out.

That's a good point about new users and it would be nice to have these actions "greyed out", but I'm not sure how to achieve this consistently with all the supported completion engines - Helm, Ivy, Ido, Hydra and native completion. Probably, the solution will be to fire an informative message once the unavailable action is chosen. Or to modify the action name with something like "action name (unavailable)"

[myshevchuk]

Do not grey out Open PDF, suggest to download PDF instead. See #176