settings: support code-generated setting dependencies
move ISliderCallback into its own header file
guilib: don't abuse and redeclare SPIN_CONTROL_TYPE_FOO
CGUISliderControl: fix SetIntValue() and SetFloatValue()
settings: add slider control
settings: integrate slider control into GUI
settings: add CSettingControlCreator implementation of ISettingControlCreator for easier re-use
settings: add CSettingCreator implementation of ISettingCreator for easier re-use
settings: make use of CSettingCreator and CSettingControlCreator in CSettings
settings: add CSettingConditions with all simple and complex conditions
settings: make use of CSettingConditions in CSettings
settings: change signature of SettingConditionCheck to include the CSetting instance instead of just its identifier
settings: adjust the implementations of SettingConditionCheck
settings: add CGUIDialogSettingsBase
settings: add CGUIDialogSettingsManagerBase
settings: make use of CSettingControlCreator in CGUIDialogSettingsBase
CSettings: expose CSettingsManager instance
settings: update CGUIWindowSettingsCategory to derive from CGUIDialogSettingsManagerBase
settings: add methods to manually put together setting sections, categories and groups
settings: add range slider control