Links xDS earlier in API v2 overview. Removes line numbers from github xDS proto links.
Modifies xDS protocol doc to more clearly define xDS at the start.
Signed-off-by: Stephan Zuercher <stephan@turbinelabs.io>
This patch adds an overview page introduced the v2 API concepts via a
worked example. Brought in the entire transitive dep set of protos from
bootstrap.proto, none of these have been cleaned up beyond the minimum
required to have them build under Sphinx.
Also added the ability to link to the underlying proto in messages/enums
from protodoc.py generated RST.
Signed-off-by: Harvey Tuch <htuch@google.com>