Fix/reindex on create product outside admin scope

[ticaje]

This fixes an issue i've come across regarding importing product's stock outside admin interface.
It turns out that when importing product's stock abroad from an interface other thatn admin back-office, a file based import process for instance, the method multiLocationInventoryProductSave is not being dispatched since it's tied to adminhtml node in the config file. 
So, this fix consists of creating a new event under global node and defining an argument to make sure inside attached method that it's only being called in this context. Then in the observer's method defined i perform the proper index table persistence, based on the product's stock related data.
An array must be defined which will be passed out trough request object, this is responsibility of the importer. Such an array must containg at least the same keys than the one obtained by:
Mage::app()->getRequest()->getPost('multilocationinventory');

Valid to say that this fix could include way much refactoring.