method already in the same file. Fixes #4273.

 * 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.

Didn't notice them and implemented something like that myself.

* Added NS_RECEIPTS to protocol namespace list.
* Show our support of XEP-0184 in caps.
* Added a big, fat warning to get_contact as this does not work as
  expected.
* There was some strangeness in our XEP-0022, it added an id tag to
  the x tag, which isn't mentioned anywhere in the XEP. And for some
  strange reason, that id even was the same all the time.
* Fixed a typo.

Someone completely broke it by trying to port it to native GTK.
However, that person didn't only break it with X11 GTK, with
native GTK it wasn't working correctly either.
Fixed it by adding lots of try/except blocks. Someone definitely
deserves to be slaughtered for completely breaking it on OS X…

* Fix helpers.py so URL is decoded correctly.
* Fix code in roster_window.py so the \0 that's alway the last file
  on win32 is ignored.

This also fixes and closes #2398.

problems.