Generate Ext.create() with dynamicly returned type.

[tomFlidr]

// ambient context:
declare interface ExtGlobalTypes {
"Ext.dom.Element": Ext.dom.Element;
"Ext.data.Store": Ext.data.Store;
...
}
declare class Ext {
public static create (className: K, ...args: object[]) => ExtGlobalTypes[K];
}

// standard context:
var store = Ext.create("Ext.data.Store", {});
// ... store is now Ext.data.Store type:-)