Remove cf_section_template().  No one uses it
Remove templating from cf_pair_find().

This breaks the server, so the next commit will add templates
back in again, in a better fashion.

We also remove the ability to do cf_pair_find(cs, NULL), and have
it return the first CONF_PAIR.  After searching the code, no one
uses this functionality.  So it's best to remove it.
Fix templating code.

Instead of hacking a reference into cf_pair_find() but not
cf_section_*_find(), we just copy the template recursively.

When we reach the end of a section with a template, we merge
a copy of the template into the current section, then we nuke
the relationship between the section and the template.

This uses more memory, but it means that templates now work
with subsections