Refactor out code duplication

When enabling/disabling a module there is duplicate code that pings WordPress.com with
the update. Abstracting this out into a method in Jetpack::toggle_module_on_wpcom().
This allows the dev on a module to simply do something such as:
add_action( 'jetpack_activate_module_monitor', array( 'Jetpack', 'toggle_module_on_wpcom' ) );
add_action( 'jetpack_deactivate_module_monitor', array( 'Jetpack', 'toggle_module_on_wpcom' )  );
Switched to passing in module instead of trying to guess module on de/activation
Merge branch 'master' into refactor-module-toggle

Conflicts:
	class.jetpack.php
Merge branch 'refactor-module-toggle'