[WiP] Fix trial expiration

Separating plan_level from community to a new table for the sake of saving some data about when communities have changed their plan levels.
Yes, and no. 
- After the last discussion about whether we should use pixels or not - I had in mind that we don't have a clear plan yet and people seemed to favour pixels.
- This design relies heavily on different font-sizes and it is a problem with em inheritance 'feature'. So, to me, this is more about whether we use rems or pixels.

I could change this to rems if we want to go there.