Refactor to MobileAccessibility.postNotification to accept other notification types

MobileAccessibility.postNotification now allows you to send
UIAccessibilityScreenChangedNotification,
UIAccessibilityLayoutChangedNotification, and
UIAccessibilityPageScrolledNotification in addition to
UIAccessibilityAnnouncementNotification.

Refactor isVoiceOverRunning and “voiceoverstatuschanged” to the more
platform agnostic isScreenReaderRunning and “screenreaderstatuschanged”
in anticipation of Android support.
[trivial] update .gitignore to ignore Eclipse project file