Add more granularity settings

I have also tried to make an update function.
However, it doesn't work yet.
And I actually don't think we should do this, because it requires loading a lot of stuff that probably isn't supposed to run in that bootstrap mode.
But anyways, here it is, in case someone think it is a good idea.

Updated, to avoid some notices.

When the length of the cid is greater than 255, the last part should be hashed.
Or else the database will return an error.

Fixed an issue with 'url' resetting the id.
Added converting old values in the settings form defaults.

Fixed the conversion of old settings.