Add persistent filesystem service

The Jenkins Stackato app is currently dysfunctional for production usage due to Jenkins requiring a persistent filesystem service (see [Administering Jenkins](https://wiki.jenkins-ci.org/display/JENKINS/Administering+Jenkins) for details on its persistence requirements and the respective configuration of the JENKINS_HOME directory) .

This pull request addresses this by adding the filesystem service for the JENKINS_HOME directory and a symlink from HOME/.jenkins (/app/tomcat/webapps/ROOT/.jenkins) to JENKINS_HOME/.jenkins accordingly.

* :warning: This is currently tested/used in a labs environment and seems to work reliably for updates via `stackato update` as well as app/instance deletion (while retaining the persistent filesystem of course)  and subsequent `stackato push` - YMMV as usual.