Eliminate need for GET_TASKS permission

Fixes Cordova error when trying to open the app from the notification bar

Added a missing comma after errorHandler

* Don't check if we are in the foreground - that happens anyway in the
sendExtras() method (https://github.com/phonegap-build/PushPlugin/blob/master/src/android/com/plugin/gcm/PushPlugin.java#L111)
* Only display a message if the message has text to be displayed

Fixes #52 and undoes #3

Use & instead of your large and error prone if statements

Fix typo: successCallback should be errorCallback

Finalize pre-3.0.0 plugin fixes

plugin submission requires a version bump even if plugin was previously
deleted (bug?)

Fix setApplicationIconBadgeNumber returning errors.

The signature of all the methods callable from JavaScript had to change
from:
-- (void)register:(NSMutableArray *)arguments
withDict:(NSMutableDictionary *)options;
to
+- (void)register:(CDVInvokedUrlCommand*)command;

The old format was officially obsoleted in in Cordova 3.0, so there is
no way around using the old one.

'arguments' and 'options' needed to use the new 'command' object.

With this new format the plugin result interface was also broken, so it
was changed to the new documented format.

This code is _not_ well tested at this point, but I wanted to get it up
for anyone having issues migrating to 3.0.

Fix for setApplicationIconBadgeNumber