fine tuning the pixel of composing panel, while issue #35 should be fixed later

git-svn-id: https://svn.apache.org/repos/asf/james/hupa/trunk@1522286 13f79535-47bb-0310-9956-ffa450edef68
prepare for the composing content, attachment and status panel

git-svn-id: https://svn.apache.org/repos/asf/james/hupa/trunk@1522287 13f79535-47bb-0310-9956-ffa450edef68