Revert "CORE-4927 More refactoring to use folder paths."

This partially reverts commit c640e97298a22c27afcdf63fe55aa82d649e323d.
CORE-4914 Added root folder check to DiskResourceViewImpl#getFolderById

Since a root folder that is listed under another root should be considered a filtered folder (such as the user's home folder that is listed under the "Shared With Me" folder, a.k.a /iplant/home), the DiskResourceViewImpl#getFolderById method will first look for a root folder to return that matches the given folderId.
Removed KLUDGE not needed anymore in GXT 3.0.6.