Add svc-map element.

Adds a new svc-map element which can be used to install
services based on an in element 'svc-map' YAML config
file format.

This change is intended to decouple elements from DIB
and allow new elements to support multiple distributions
(with various service naming schemes) without having to
constantly maintain DIB's various bin/map-services files.

This patch ensures all of the YAML files are compiled into
a single file without namespaces.  The YAML compilation
process occurs during image creation time and errors if
conflicting mappings are found.

Change-Id: Id11433ea342aace71a358936a7ca3151ec11d506
Merge "Add svc-map element."