Add support for array templates to the client-side templates extension

[vadave]

Resolves #1775 by introducing <template-engine>-array-template renderers that can be used to work with APIs returning arrays of data.

[1cg]

beautiful, great solution!

[biocarl]

Are you aware that at least moustache templates allow to reference the current context with .? So when passing in an array (e.g. [{"a":2, "b":4}, {"a":3, "b":4}] you can simply do:

{{#.}}  
    <h3>{{a}}</h3>
    <p>{{b}}</p>
{{/.}}

Resulting in

<h3>2</h3>
<p>4</p>
<h3>3</h3>
<p>4</p>