fix #11676 dijit.form.Select uses a custom setStore...

dijit.form.Select uses a custom setStore rather than select.set('store', store);

Updated the API for _FormSelectWidget to allow the use of set('store'...).

Marked setStore as deprecated and added doh unit tests.

I call the private _deprecatedSetStore from set. Much of the code in `_deprecatedSetStore` is marked to be removed in 2.0. Once it is removed we can unify the api to use set directly without worrying about legacy stores.

[fixes 11676](https://bugs.dojotoolkit.org/ticket/11676)