fix #6: lazy initialization of cloud jenkins storage implementation

- workaround for timing issues that lead to failed JNDI lookup of
  document service
- added logging to indicate when FileStorage is used instead of
  ECMStorage
removed logging jars provided by HCP runtime from web archive

- debug logging did not work reliably, some categories worked and
  some did not work
- Jenkins manages JDK log level configuration which is plugged 
  in series to HCP log level configuration
- Jenkins contains slf4j-jdk14 adapter that redirects slf4j logging
  to JDK logging which is redirected again to HCP logging
- after removing logging jars from cloud-jenkins war at least slf4j
  logging in our own code shows up according to log level config
  in cloud cockpit
Merge pull request #7 from stephanme/master

fix #6: lazy initialization of cloud jenkins storage implementation