-Create application->switchManyWindowsBack() method
-Create equivalent to empty window enum class
-Remove stored prevWindows variables
-Add bottom bar to empty window (equivalent to allEvents)
-Repair going back to previous windows functionality
-Repair switching window (with empty events DB)
-Add EventShift value to event records time
Implement adding record to db
Implement Removing elements from DB functionality
Implement Update element in DB functionality
Implement Get elements by date time period
Add time zone field