iOS only: use invoke url only if it starts with fb
remove unused FREContext
use try catch to avoid crashing the app
implements publish install for Android
Fixed a crash on iOS when not using iOS 6 system account.
Updated .gitignore
Fixed rare login bug on iOS 6.

Bug: an iOS 6 device would have the app set to "ON" in "Settings -> Facebook" but the Facebook SDK would return an error as if the app was "OFF" (ie. blocked by user).

Solution: call [FBSession renewSystemCredentials] when initializing the ANE. That requires killing/restarting the app to solve the issue.
Added some try/catch and other checks to fix some crashes on Android.
fixed problem the ane was causing on ios notifications
Updated Android code to handle cancel event properly
Update to prepare for iOS 7 and clean a bit the project.

* Updated Facebook iOS SDK to 3.7.1.
* Replaced Facebook iOS SDK sources with FacebookSDK.framework in Xcode project.
* Setup build.xml and platform.xml to package FacebookSDK.framework with the ANE.
* Setup Facebook iOS SDK as a git submodule for easy update.
* Migrated Xcode project to ARC.
* Reorganized Actionscript folder to have only one project.
* Updated the ASDoc.
* Updated extension.xml and platform.xml for AIR 3.8.