Make date_added a default feature

[Difegue]

It's been there long enough and most people seem to want to use it for sorting, so it certainly deserves the promotion.

It'll likely be a separate database field instead of being in the tags like it currently is, which allows me to give it better formatting as well (proper dates instead of a UNIX timestamp? wow!)

[CirnoT]

How do you see it working with alternatives (such as EH plugin's timestamp field)?

In addition, while this is currently possible to replicate (using Display Options ability to customize columns), LRR does NOT remember sorting configuration when leaving page, so this would need to be handled better before any kind of sorting can be useful on web.

[Difegue]

I don't; The field will only handle the time the file was scanned/added to the server, every other kind of timestamp is still up to the users.

I forgot to create an issue for storing sorting/last search in localStorage, but that's a survey req I'd like to tackle as well.

[Difegue]

I've added specific formatting for date_added (and timestamp) in the webUI to show them as human-readable dates.

To keep backwards compatibility (and also because it's easier lmao), the date is now added by default in the tags field.