pmd plugin in master pom

[Jurgen Lust]

Hi,

I've added the maven PMD report plugin to the master pom, using the 'basic' and 'unused code' rulesets. It adds 2 extra reports to the project website: a copy-paste detector report, and a PMD report.
What do you think? I'm thinking we can start with the basic rules, and as those problems get solved, add some extra rulesets. I think these automated code audits are very useful...

Jurgen