* Use argparse instead of optparse for standardised help output, options
and a much cleaner code structure
* Look up pkgdata directory automatically so the user doesn't have to
specify it
* Use standard logging
NOTE: this does mean a slight change in syntax - if you do want to
specify the pkgdata directory (usually only necessary if you're calling
it from within the build process) you need to use the parameter -p (or
--pkgdata-dir) and specify this before the command, not after it.
