Settings pk

[rnwgnr]

Not a functional addition, but rather a change for consistency:
Add a primary key for the settings table as well.

This will reduce potential misbehavior as setting keys can no longer be set more than once.
This update will fail on installations where the settings are already messed up.

[ildyria]

Looks good to me.

However this PR will probably wait for other items to be added into Lychee v3 as it switching version just to add a primary key into a table seems a bit small.

[rnwgnr]

However this PR will probably wait for other items to be added into Lychee v3 as it switching version just to add a primary key into a table seems a bit small.

Yeah, of course. I may have some rather specific additional features in the next days, even though i`m not sure if these are interesting for "the masses". ;)

[rnwgnr]

The setting key 'full_photo' is already implemented but not present in the settings table.
Add this key to the settings table to allow editing using the 'full settings' page instead of messing around with a db tool.