Karaf improvements, Fetchmail works

* introduced base class for LiveTests, but no plugin configuration yet
* moved feature tests to it's own class
* james-server-fetchmail feature installs and works as expected

git-svn-id: https://svn.apache.org/repos/asf/james/server/trunk@1444534 13f79535-47bb-0310-9956-ffa450edef68