(proxy) move acl part to separate file and add option for custom templates, closes https://github.com/opnsense/core/issues/802

We do have a config.xml default, and we don't need a second default
that pops up every time the old layout is cleared.  On top of that
the old layout could never be cleared again, so it only dealt with
an empty config.xml scenario which we don't have.

This reverts commit f44b7e0c.
Ad found an irregularity, so we back this out and look for a
better fix...