Ignore "sticky" local group settings when publisher groups are present

I created an open group for http://www.windley.com/, which embeds the H client. My expectation was that it would be the default group for visitors to that site, overriding whatever sticky selection the client is remembering.

That doesn't happen but seems like it should. Otherwise, as @seanh noted elsewhere:

> No one who has not launched h on example.com before will ever have example.com's open group as their default group, when they visit example.com for the first time, will they?

And no one who visits windley.com and defaults to Public is likely to discover the open group there in order to set it as the sticky default.

As a user of a site that provides an open group, I want to discover that group when I visit the site, so that I can read it and maybe interact with it.

As a publisher of a site who is providing an open group, I want my visitors to discover it for the same reason.

Start by tracing the H client's group-selection behavior, focusing on how remembered local settings interact with publisher groups. Done means a site's open publisher group is discovered and used as the default for visitors instead of an existing sticky selection, including first-time visitors.

Written by the indexing model from the issue text.