documents: file service is meant to be a singleton (so use getService) and store on the class

(integrated from komodo (trunk) change 81085 by toddw)

git-svn-id: http://svn.openkomodo.com/repos/openkomodo/trunk@13297 b87d16e7-d29f-4ee1-b5ec-817d645d335f
file service: use a lazy property

(integrated from komodo (trunk) change 81086 by toddw)

git-svn-id: http://svn.openkomodo.com/repos/openkomodo/trunk@13298 b87d16e7-d29f-4ee1-b5ec-817d645d335f