Changes

*[new] Added warning dialog when a session is disabled

*[new] Added Backup feature for daily/overview graph settings

*[fix] Improved support for PrismaLine bilevel modes

*[fix] Selected event not showing in PRS1 devicess

*[fix] Viatom now imports files with .dat extension

*[fix] Graph combo box updated

*[fix] Allow Graph and Event combo boxes to remain open after changes.

*[fix] Overview display of ResMed Oximeter events now works.