Java datamodel changes to support find files API in general data source, and not just image
vs_open: Ensure img_info is non-null

The tsk_vs_open function was assuming non-null input.  This caused a
segfault in the dos opening function in a case where tsk_img_open's
results weren't checked.

I missed that check in early development on an app.  I probably won't
be the last to do that.

Signed-off-by: Alex Nelson <ajnelson@cs.ucsc.edu>
java data model: propagate fs obj id for local data sources also when adding virt dirs
Fix setting parent_path for carved and local files/dirs.  Use parent's parent_path and name.
correct / in parent_path for local files
Merge pull request #189 from adam-m/master

java datamodel changes to support find files API by data source Content and not just Image
Merge pull request #190 from ajnelson/ensure_img_data_in_vs_open

vs_open: Ensure img_info is non-null