Add WIP support for Language, Rotation and MemoryCacheSize in Settings.
Adds missing SelectionModel for use with setting language.
Adds additional values to Settings for storing new values.
Adds SettingsDialog()::loadSettings to restore values via Settings class.
Refactors existing SettingsDialog to allow placement of Save button to the side.
Standardises some member data names.
Adds new buttons ready to SettingsDialog for new values but doesn't add connections.