bandwidthd belts and braces checks when generating conf

Forum: http://forum.pfsense.org/index.php/topic,68477.0.html
Allows users to put "0" in various fields and have it come through validly into the bandwidthd conf file.
Previously bare "0"s would appear in the conf file, which were wrong.
bandwidthd version bump
bandwidthd version bump
bandwidthd version bump
Merge pull request #565 from phildd/master

bandwidthd belts and braces checks when generating conf