SettingsManager, touch event and touch plugin upgrades

• Made TouchManagerPlugin a more explicit class in its own file
• TouchManager now allows plugins to modify touches before and after they're processed (e.g. useful for TangibleEngine, which needs to convert touches from Touch to Fiducial)
• SettingsManager can now be subclassed and initialized more easily
• SettingsManager can now be configured to load a specific json file from any location
• All touch events in TouchView and TouchManager now follow Cinder's getSignal...() naming convention (mDidBeginTouch is now getSignalTouchBegan())
• Updated samples to reflect new changes
• Removed outdated or redundant samples