Update pages to mention git instead of svn

git-svn-id: https://svn.apache.org/repos/asf/karaf/site/trunk@1551858 13f79535-47bb-0310-9956-ffa450edef68
Announce the move from SVN to Git

git-svn-id: https://svn.apache.org/repos/asf/karaf/site/trunk@1551859 13f79535-47bb-0310-9956-ffa450edef68
Add articles links about what coming in Karaf 3.0.0

git-svn-id: https://svn.apache.org/repos/asf/karaf/site/trunk@1551860 13f79535-47bb-0310-9956-ffa450edef68