Removed TODO marker for unimportant task of which it is also not
immediately clear how to implement it.
Removed obsolete TODO

I originally added this TODO to suggest a nick name when adding a new
chat room. However, in the mean time I have decided to not allow nick
changes upon joining a new chat room, so this solution is now obsolete.
Fixed bug where command without parameters would not be recognized.
Log exceptions caused by command execution and added markers for improvements.
Fix incorrect registration state in case user cancels IRC connection because of certificate issue.
Primitive implementation of presence watcher for Contacts.

A primitive initial implementation for periodically testing the presence
of contacts by using IRC's ISON query. Currently using a period of 60
seconds, it will check with the IRC server whether or not contacts are
online. Contact presence change events will be fired for each of the
results, both online and offline. For presence changes, the contact list
will be updated accordingly.

Additionally, presence update events will also be fired in case an
ERR_NOSUCHNICK is received. This indicates that something assumed that
the contact was online, but it turns out that this contact is actually
offline.
Improved contact presence support:

1. Support for long lists of user names by sending multiple queries.
2. Created FIFO list for nick sets. Each nick set is exactly the content
of 1 query, such that we can handle the RPL_ISON events by comparing
expected nick list with actual nick list.
3. Update presence upon receiving QUIT, channel join.
4. Escape for case when unexpected RPL_ISON is received. (i.e. list of
expected nick sets is empty)
5. Implemented subscribe, unsubscribe methods for
OperationSetPersistentPresence.
Tweaks.
Make submittedMessage volatile, just in case.
Converted sorted set to list, since we have a (already sorted) list
of nicks that we query for in a query message. (+ misc improvements)
Clean up.
Watch list now persistent over (dis)connects.

The watch list is now persistent over disconnects, such that
disconnecting and reconnecting to the IRC account will not lose the nick
watch list content. Of course, we will still lose all contacts when
Jitsi is shut down, because the contacts are volatile contacts.
Fix line longer than 80 chars.
Update presence status of a user when a message/notice/action is received from this user.
Fixed some warnings.
Introduced constant for end of ME command prefix index.
Implemented (approximate) computation of overhead to get most nicks in single ISON query.

The computation is approximate because I've added 10 chars overhead in
the computation, since without the 10 chars there were some spurious
nicks missing even though these nicks were online. The number 10 was
arbitrarily chosen. It seems to do the trick, though.
Update nick watch list on nick change.
Added support for IRC contact renames on nick change event.
Created AbstractIrcMessageListener that implements support for connection management.

Created an abstract class which implements the base support for
responding to quit events and errors. This only needs to be overridden
in cases where additional action is required.