V2.2: Import Page, All Items Page, Fixes and Improvements

New Features

Delete UploadApply and GPOImport pages, and replaced with new and greatly improved Import page.
Added basic Logger class and some calls to it throughout the project.
Added All Items page, which shows all items regardless of DT or if they're in a folder, as long as they're not in the trash.

Changes and Improvements

Increase LIMIT from 50 to 100 when loading more items.
Backups.razor now uses Fastest instead of SmallestSize.
Renamed pss_upload to pss_import and updated appropriate variables, constants, and comments.
GenerateThumbnail now ignores error if can't delete its tmp file.
NavMenu buttons now turn blue if that button's page is active.
Address miscellaneous build warnings.