gt-property-ng module update

This pull request is comprised of two commits; one for code changes and one for formatting and other non-functional changes.

The first commit is an update to the gt-property-module. It cleans up the syntax to better match the ContentDataStore tutorial (rather than AbstractDataStore) and enforces directories containing property files as input to PropertyDataStore. Test cases have been updated to test/support this new functionality. Where possible, warnings have been resolved.

The second commit does not contain any functional changes to the module source code - It removes unexpected whitespace, maintains a consistent indent level, removes extraneous imports, updates header dates, and fixes a few comments.
Depends on if this commented code needs to be here; It was carried over from the origional implementation, and I am not entirely sure what it does (Functionality seems to be replicated by the previous lines). If this line is important, then it and the above lines should be uncommented; if this line should remain commented then so should the above lines; if this line is not important then it and the above lines can be removed.