Added more comments. Also the filter now demonstrates how to
1) read configuration parameters
2) react to queries and replies
3) handle shared filter data
4) print diagnostics output
5) add log entries
As the filter is already built and moved to the library directory,
it is immediately usable. This should be helpful with assignments.
See script directory for method. The script to run in the top level
MaxScale directory is called maxscale-uncrustify.sh, which uses
another script, list-src, from the same directory (so you need to set
your PATH). The uncrustify version was 0.66.
