We had a few syntax errors, bad links, redundant references, bad

database values, and incorrect configuration settings for the

documentation that led to error output when building the Review Board

manual, and a handful of harmless but annoying warnings due to missing

image state when simulating data for the API documentation. This made it

hard at times to determine whether new changes to the documentation were

correct, particularly for new contributors to the documentation.
This change fixes the errors within the documentation and the

configuration options for the manual, and disables the logger that's

complaining about missing image files (which don't otherwise impact us).

It also updates us to Sphinx 1.7, which solves a couple of other

warnings with references and unveiled others.
There is one error remaining, which has to do with how Sphinx is

attempting to introspect the webapi resource registry in a way that's

causing an attribute error. This must be addressed in Djblets.

Documentation built without errors (except for the registry one) on

Sphinx 1.7.