Consistent use of material theme across specs and impl project docs

Consistent use of material theme across specs and impl project docs

This applies the same material theme and build dependencies to the
implementation project documentation as used by the specs. It thereby
creates a consistens look-and-feel across both set of docs.

Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>
Change-Id: I16f8bf2b500260549bab8b21d1ab58d76cb103c6