- Do not crash because of low disk space
- Notify the user whenever it happens
- A few functions now return a boolean instead of nothing
- Config.silent_set is Config.set_and_save without toggle and returning
  strings. It is used whenever we don’t need set_and_save
- Config.set_and_save now returns a tuple (that can be passed directly
  to core.information())

TODO: display the precise error to the user (instead of “unable to…”)

- Refactor the message handlers to be more readable
- Add a group_corrections tab-specific option (#2229)
- Fix issues with /correct in private tabs and conversation tabs

and do not read the whole log file for the last lines.

(instead of chaos)

- New option load_log defaulting to 200 to indicate the number of lines
  to be loaded
- It’s still very raw, and the format of the message does not match the
  format of the normal room history, for example
- Works in the Private chat, MUC, and Conversation tabs

Thanks to labedz <github@labedz.org> for the original code

Fix a little crash, fix the authentication process (was not working with prosody, because it was wrong), fix the sending of the vcard (was broken too, but ejabberd doesn't complain...)