This commit adds a new sphinx extension that inspects the nova code
and adds information about the existing versioned notifications to
the nofitications devref. This way the devref is automatically kept
up to date with relevant information.
Partially-Implements: bp versioned-notification-api
Change-Id: If65d5d81e26cb2b4a9f57a8c7d37d3de310ebe00
752765cfd6