Added loadConfigs method and event to the store and rs addons.

Some RS addons get the host (store) configuration when they are initialized.
However the same addons can potentially modify the app/host configurations while discovering resources in the filesystem (i.e. dynamically adding dimensions or configurations from resource bundles), leaving them with incomplete or inconsistent data.
For this we have added a public method "loadConfigs" to the resource store and the addons, and we've made the store to fire a "loadConfigs" event when it's configs are loaded/changed, so addons can subscribe to and update their configs if they need to.