Array structure too limited in layout

[jvalkeal]

This layout feature request is mostly related to JsonGroovyBuilder when layout is build.

When you do:
items(){
...
}

json looks like "items:{}".

If you do:

items(){
...
}
items(){
...
}

json looks like "items:[{},{}]".

Remove limitation that case like this needs to be array even if there's only one object per array. This allows JS to play nicely with JsonGroovyBuilder. Also check other places in layout structure where similar change make sense.