holy diff batman!

 * set default file type for avatars centrally
 * remove client side decision logic determing if a avatar loookup shall happen for a groupchat contact or for a normal contact
 * remove unused method (this one was triggering the traceback in #5461)

 * remove js from some headers
 * set coding:utf-8 to allow real names in headers

 * Remove some licencing problems
 * To do: same for images
 * See #4200

we have that in all files. To at least lesser the confusion a bit, add
vim tags for that.
Additionally, fix wrong #! in a few files.

don't request jabber:iq:last and jabber:iq:version to real jid in a (semi) anonymous room, even if we're moderator and we know the real JID. Fixes #3454

Sorry, bct, but I think it is to early to merge that as it completely
breaks. It seems nobody in gajim@conference.gajim.org considers it
usable yet.
I don't know if you got asterix' ok for it and I'm sorry if I reverted
it now although you had his ok, but having broken trunk is very
contra-productive. I think it was just too early to merge.