added cache and make sure we are not fetching invalid path

[christophe-g]

Just to make sure we are not fetching url when the path is not ready (e.g. "/myPath/[[resourceId]]" and resourceId is not set).

Also added a way to cache path to avoid async response when a path has already been fetched.

I did put the cache behaviors in myBehaviors namespace. This can change of course if you plan to use another namespace for this component.

[sbeleidy]

Awesome @christophe-g ! Thanks for the contribution!

Will try to review it get back to you soon.