settings: add ISettingsHandler
CPlayerCoreFactory: implement ISettingsHandler
CRssManager: implement ISettingsHandler
CUPnPSettings: implement ISettingsHandler
CAdvancedSettings: implement ISettingsHandler
CApplication: implement ISettingsHandler
settings: add ISubSettings
CSettings: now we can savely call Clear() again from the destructor
settings: move skin settings into CSkinSettings
settings: move source settings into CMediaSourceSettings
settings: move view state settings into CViewStateSettings
settings: move watched and video settings into CMediaSettings
settings: don't forget to unregister subsettings and settings handler implementations
[win32] update VS project files
[osx/ios/atv2] - sync xcode projects
Merge pull request #2445 from Montellese/settings_cleanup_3

settings cleanup (CSkinSettings, CMediaSourceSettings, CMediaSettings and CViewStateSettings)