Run some code duplication analysis

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1632403 13f79535-47bb-0310-9956-ffa450edef68
Misc code cleanup2

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1632404 13f79535-47bb-0310-9956-ffa450edef68
Refactored assembly building logic with slightly more powerful building blocks and a little more correctness

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1632405 13f79535-47bb-0310-9956-ffa450edef68