Fix maven compilation

The pom.xml file was there for decoration exclusively, since it didn't
compile anything, it just added everything as a resource
Allow sending message replies to things that aren't players or console

As requested by a craftirc user (craftirc runs commands), but I heard
people want to run this through rcon too.

Also, copypasting the whole function to handle slightly different
parameters is not a great idea. Just saying.
Refactor the ping command to use threads

Oh the irony of writing a plugin to monitor server lag, then add a
command that blocks the game thread for up to 10 seconds, while waiting
on a "while" loop for an external process to exit. And... this causes lag!

Bonus points for using the word "exponentially" to describe the time
complexity of an operation that involves sending a constant number of
packets and getting the same number of replies.

I removed the 10 packet limitation and changed it with a warning saying
that it might take a long time. Feel free to change this part to
something else - since this command uses nearly 0 cpu time, I felt it
made no sense to block this feature.

(Heh, "block")