Fix broken test of marshalling tree in accordance with:
https://trac.openmicroscopy.org.uk/ome/ticket/12474

The test now correctly uses a read-only group and thus also asserts that
the received permissions reflect that
Fix permissions for tree projections

Makes use of a cache to avoid repeated querying

Temporary fix for:
http://trac.openmicroscopy.org.uk/ome/ticket/12474
Fixed bug where project permissions being used in place of dataset
Restored normal permissions parsing in tree

Convert the permission type in the workaround instead
Removed unused import
Using local cache and updated query
Type and remove print statement
Set Dataset permissions rather than Project permissions

It is possible that the permissions of the Project are different than
the permissions of the Dataset.  In order to not have "permission
denied" error dialogs pop up when this situation is run across this
change needs to be made.  It follows the changes already made to the
permission loading semantics from gh-2844.
Merge pull request #2872 from dpwrussell/rebased/dev_5_0/projection_perms_check_fix

Correct permissions when using permission projections (rebased onto dev_5_0)