Binding API issues

[ddworak]

• showIfElse doesn't provide nested interceptor
• repeat is usually used with a nested interceptor and produce
• repeat without nested is the default which is not very common use case

[Starzu]

You may also consider showIfElse with by-name arguments.

[ddworak]

@Starzu we did https://github.com/UdashFramework/udash-core/blob/master/core/.js/src/main/scala/io/udash/bindings/Bindings.scala#L88 :D