Add actor account support for 1.0.0

[garemoko]

Fixes #19

This is what it ends up looking like:

Or before you enter the values:

[garemoko]

Note that I deliberately did not rename "agentValue" to "agentEmail" for two reasons:

1. Backwards compatibility. TinCanViewer.js needs to work with systems that have used the code with their own html UI (like Watershed) and may not yet have made relevant changes to take advantage of the account functionality.

2. This field could be used with openid and mboxsha1sum too, and in fact it would be a trivial (but out of scope of this PR) change to make that work.

[garemoko]

Also note, regarding "else cuddling" - a lot of the existing code in TimCanViewer.js does cuddle elses so I followed that style.

[garemoko]

This line ends up being duplicated to avoid overly complex if conditions.