Add support for publicly-accessible LocalSites.
LocalSites have always been locked down to members of the groups, but

there are advantages to allowing for anonymous access when simply used

for partitioning of a server by teams/organizations.
This adds a public flag to LocalSite. If set, non-members will be able

to access anything that's considered public within the LocalSite. This

essentially gives it the same behavior as a standard site.

Unit tests pass.
Tested on RBCommons. I was able to access a public team, post review requests,

and post reviews, without being a member of that team (and without being an admin).