Add Kotlin extension functions support

[vmutafov]

Related to: #1468

Currently, the only way to use Kotlin extension functions of a given object type is to use the Kotlin compiler-generated utility functions.

We should provide an easier way to use them.
For example, if we have an extension function of ArrayList:

fun ArrayList<String>.someExtensionFunction(someData: Int){
}

In JS/TS we should be able to use it like:

let arrayList = new java.util.ArrayList();
arrayList.someExtensionFunction(42);