Fix menus - Githubissues

OK, here is the patch that fixes the menus that I would like us to merge before the next stable release. As usual, once I started poking around all sort of other minor irritations showed up so I included a few other fixes as well. But in general:

Removed Import and New Album from smart albums (kept Upload since that one at least works)
Fixed the code introduced in #253 that moves some of the button functions to the context menu on narrow screens. It added them unconditionally, even if the particular functionality shouldn't have been available (either due to the public mode or smart or tag albums)
Removed cover image selection entry from the context menu for smart and tag albums since it doesn't work there
NSFW button was not available for tag albums even though it does work there
Import via GUI in albums view would often try to load non-existent album "0" when finished. I could've changed it to "unsorted" but I think it's better to simply reload the albums view since that's where the user was to begin with.
Under unclear circumstances (race condition?), the info sidebar could be empty for albums. Turns out there was already code in place to handle that but a condition got reversed in #253, presumably accidentally.

LycheeOrg / Lychee-front

Fix menus #278