Ready for Review: added an cli option to delete an album with its pictures

[Riscky]

Status: Done, pls review

Added a command line option to remove an album, including its pictures. Use pxl delete "Album name" to delete its pictures from the file hosting and remove the album from the state, in that order. If the given album name does not match any known album the operation is cancelled.

Biggest drawback of this implementation is that the pictures are removed from the file hosting before the site is rebuild and deployed, leaving a window in which the album appears to have missing pictures. The user is warned of this issue after the operation finishes.

[duijf]

Hey thanks for the PR!

Please:

• Make the typecheck pass
• Update the description of this PR with your general approach/tradeoffs etc
• Mention the status. Is this ready to merge or are you still working on this? Do you want a review?

[HugoPeters1024]

@Riscky Could you also please rename (and potentially squash) the commits to a "subject: short description" like format to make it match the rest of the commit history?