Completely remove DW upgrade mode

Since DW upgrade mode seems to unleash passions, lets try to find a way to get it of it completely.

The idea is to have both modes more or less enabled:

• DW is always enabled on subwikis and will show up if there is something to do (i.e. if it's not already been done from main wiki)
• subwikis are always listed for upgrade in the main wiki but you don't have to do all of them to continue

It has the advantage of removing a few hacks in DW code for which I was not very happy.