Split the data structures for SSSD.
Simplify the schemas of different access providers

It's easier for the user to have one field dedicated to LDAP and another
one to "simple" providers.
Remove dummy contributors and old dependencies.
Include the TT files in the packaging.
Add TT files for rendering the SSSD configuration.

SSSD has lots of options and lots of subsections.  We split the
configuration rendering in many small templates.