Miner Callbacks

Implemented the concept of callbacks for the Miner to be notified of
modifications on nodes. An example of the usage of callbacks was added
to the shell.
Accomodated query to new table name
Adding my.cnf to ignore
Just read one wikilink per line in discography, because otherwise you
will be reading things like "with The Outlawz" or "with JayZ"
Making the node attribute private (for whatever that means to Python)
Use the callback to report modifications on the node that has been
processed by a plugin