Update copyright and license information
Add MobileAccessibilityNotifications to store notification constants
Adjust behavior of MobileAccessibility.updateTextZoom and MobileAccessibility.getTextZoom

Adjust behavior of MobileAccessibility.updateTextZoom and
MobileAccessibility.getTextZoom so they both return the correct updated
zoom value to a callback method.

Adjust behavior of isTalkBackRunning and isVoiceOverRunning so that
they return true only for the appropriate platform.
Update documentation