Add list of last rooms

[tweakimp]

Pretty straight forward: give me a list of the rooms I have been to. Click on a room name to join the room. Maybe show how many people are already in there.
I don't want to type my super secret 34 letter room name every time :)

[t-mullen]

Would being able to change the default room in preferences work? (For the short term at least)

How many super secret room IDs do you need to store xD

[tweakimp]

Maybe store last 5 or save them to a 'favourites' list manually via the room menu

[t-mullen]

The last room joined will now be the default as of 4.1.0.

I think this is good for most usecases, so leaving this open and backlogging for the "favourites" idea.