Change package and file names for file system to inline with jcr implementation for the photark components

Currently the file system implementation has package name:
org.apache.photark.filesystem.impl

change it to:
org.apache.photark.filesystem.services
to inline with jcr implementation of the photark component interfaces.

Also change the file name to be prefixed with FileSystem

Code review:
http://codereview.appspot.com/1143043/show