Add `Set` to `each` block

[thsaravana]

Each block resolves to only List and Map. I guess we should show Set and may be other collections. Go through Handlebars docs and see what's all are allowed.

[thsaravana]

I checked the code for Each in Handlebars Java: https://github.com/jknack/handlebars.java/blob/master/handlebars/src/main/java/com/github/jknack/handlebars/helper/EachHelper.java

It seems the entire Iterable is supported. So we need to handle this in a different way, rather than handling it for List and Set.
Also, during this we can add support for @key, @index, etc...

[thsaravana]

So it appears that each allows Iterables and any JavaBean. You can just put an object in each, and it will iterate over all the properties in the object.