Autocompletion now works with nicks in the current context, improvements

Changes:
- New ID available in every page: #nerdz_nick, which contains the nick of the current user.
- Completely removed the 'preferred protocol' option. RIP.
- The desktop notifications are not triggered anymore if the current page has the focus.
- The autocompletion works with nicknames in the current context, using the '@' character. Supported contexts are the comments and the PMs.
- Optimizations.