Update Backup Settings Class

Re-implement and optimize backupsettings. Proceed in three phases:

Phase 1: Move code so that backupsettings is a self contained class capable of both reading and writing changes to settings. At this stage, it should be compatible with the existing class to avoid making unnecessary changes in the backend.

Phase 2: Once that's complete, then refine the GUI and frontend classes to take advantage of the new functionality.

Phase 3: Modify the folder and excludeitem classes and related backend methods.