- when a new contact with higher prio connect, detach session from chat control. Fixes #5021
 - don't re-use a session that was for another sessin

Tests are more than welcome!

-Specify separation for 'gc_nicknames_colors' option.

 * 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.

attach resource to sessions so that only the relevant sessions are terminated when a contact goes offline

this way we don't get multiple tabs when the remote user moves to another resource.

fixes #3961

fixes #3950