Lots of small updates to base pom

- Upgrade surefire plugin to 2.14 (from 2.13)
- Upgrade pmd plugin to 3.0.1 (from 2.7.1)
- Upgrade jacoco plugin to 0.6.2 (from 0.6.1)
- Upgrade dependency plugin to 2.7 (from 2.6)
- Downgrade release plugin to 2.3.2 from 2.4 to fix git local checkout regression
- Upgrade mavanagaiata plugin to 0.5.0 (from 0.4.1)
- Upgrade maven-duplicate-finder-plugin to 1.0.4 (from 1.0.3)
- Update guava dependency version to 14.0 (from 13.0.1)
- Update objenesis version to 1.3 (from 1.2)
- add build helper plugin 1.7
- reactivate mavanagaiata plugin
- ban guava versions before 10.0.1 (old r0<x> versions)
- ban org.eclipse.jetty.orbit:javax.servlet (use javax.servlet:javax.servlet-api)
- ignore duplicate classes in org.jruby:jruby-complete
- make fork mode for surefire configurable using fb.test.fork-mode. Default is 'once' (was 'always').
- skip mavanagaiata plugin when no git repository is present
- skip existing license headers when running license:format
minor doc fix
pmd rulesets are now organized slightly different