Allow SVG siteLogos to be specified as data: URIs

The only legitimate MIME type for SVGs is "image/svg+xml", but our whitelist
contained "image/svg" instead.

As a result, data-URI encoded SVGs were not allowed as the siteLogo.
Updated FreeBSD setup notes.

- FreeBSD 10 does not include GCC in the base system
- 'pkg add' assumes the package is available locally
Restyle / rewrite example RP
Log events (function invocations, callbacks, etc.)
Improve logging of errors
Add links to switch shim location
Allow custom shim hosts and work without Express
Verify assertions
Merge branch 'pretty-example-rp' into future
Merge https://github.com/stevejarvis/persona into future
Merge branch 'fix_datauri_svgs' into future