Now it scrolls horizontally of 1/4 the size of the input

(and add the pep events and invites to it)

(also add colors to the /info command in MUCs)

fix #2296

fix #2227

(e.g. “/join @conference.prosody.im”)
- If the current tab is a MUC the @ prefix is mandatory as there is no
     way to tell if the user meant a room name or a domain.

- If it is not a MUC, then the @ prefix is not mandatory (but works
  anyway)

any character beyond 0x110000 does not exist and should be dropped

(use new default directory, install the plugins as a separate
python module…)

(also add outcast to the completed roles)

(Except in MUC, where we check the User object for that)

(introduced in 686352d2, because a
nick bookmark can now be None)

The parser now handles text with multiple style attributes
(e.g. bold, underlined and red text).

When an external (or internal) event may cause the order of the
cache to be modified, or new elements to be added, schedule it
for a rebuild. Otherwise, don’t, and only rebuild it when
refreshing (that should improve refresh speed a lot).

Also, if the position in the roster is further than the total size
of the roster, go back to the top instead of displaying an empty
window with “+++”.

(do not encourage people to copy the plugins)