Add .pmd files to svn:ignore.

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/project/trunk@1492875 13f79535-47bb-0310-9956-ffa450edef68
Cleanup of HC parent pom; added optional Clover profile; dropped Maven 2.x support

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/project/trunk@1493568 13f79535-47bb-0310-9956-ffa450edef68