update maven plugins

maven-gpg-plugin to 1.6
maven-javadoc-plugin to 2.10.1
maven-jxr-plugin to 2.5
maven-bundle-plugin to 2.5.3
findbugs-maven-plugin to 3.0.0
maven-source-plugin to 2.4
maven-release-plugin to 2.5.1
maven-dependency-plugin to 2.10
maven-jar-plugin to 2.5
maven-surefire-plugin to 2.18.1
maven-site-plugin to 3.4
maven-install-plugin to 2.5.2
maven-deploy-plugin to 2.8.2
maven-compiler-plugin to 3.2
maven-clean-plugin to 2.6.1
wagon-ssh to 2.8

Add comment about maven-resources-plugin 2.7 as it errors currently if
upgraded.