Add wrapper storage backend
Add mechanism to allow apps to wraper storage classes
manage creating and wrapping storages in it's own class
merge master into storage-wrapper
Storage wrapper: provide access to the wrapped storage
storage loader needs to be accessible by apps
add test cases for Mount
use a getter for the storage loader to ensure the instance is created
move storage wrappers to their own namespace
fix storage wrapper namespaces
Merge pull request #3635 from owncloud/storage-wrapper

Give apps the option to wrap storage backends