Allow elements to include skeleton config

Copies all templates found in the root of any element into the
default template location.

These templates will be filled in from heat metadata by
os-config-applier whenever it is run.

Update keystone to install templates in this way as an example.

Change-Id: I0be0a79a431e9ba5b80e84f130c48d5ce8b100ae
Co-Authored-By: Tim Miller <tim.miller.0@gmail.com>