[FIX] Templating: clone the render fn and consider binding context

When using a TemplateControl as template for an aggregation in the
databinding framework it needs to clone the render function otherwise it
simply cannot render anymore.

The second issue fixed by that change is that the templating now also
considers the binding context of the root element when used inside an
aggregation. This allows to use the TemplateControl also with relative
bindings and not absolute ones.

Change-Id: Ie178510304f0f24c0da5ee6beb29a5a3aff727d6
Merge "[FIX] Templating: clone the render fn and consider binding context"