Remove rule to perform a git submodule update on build

This does not work on OpenShift where the build happens
from a directory that is not a Git checkout

It also avoids resetting submodules during a build
where there have been intentional changes in the submodule
during development.
Change icons field in /siteinfo/:domain response from a map to an array

Previously the result used a dictionary of icons with "$WIDTHx$HEIGHT"
as a key. However it is possible that multiple icons with the same
dimensions are found.

Returning an array with 'width' and 'height' properties is also
a little easier for consumers to parse.
Add a test for the /siteinfo/:domain endpoint