[#2] Import default checkstyle/pmd configuration

The initial checkstyle configuration is the one retrieved from
https://github.com/checkstyle/checkstyle/blob/master/sun_checks.xml
(commit 788f87d from Oct 5, 2013). A subsequent commit will introduce our
modifications.

The initial PMD configuration references the default Java rulesets that the
Maven PMD plugin would use. See:
http://maven.apache.org/plugins/maven-pmd-plugin/pmd-mojo.html
[#1] Initial public commit of source code