Add ability to mark profiles as public

[cdriehuys]

Feature Proposal

As we discussed, it is easier from a user perspective to restrict access to specific profiles rather than on a per-user basis. To accomplish this, we would need to add a field to mark profiles as public, and a field to the Know Me user accessors that allows access to private profiles.

This will also allow us to remove the KMUserAccessor.can_read_everywhere field since the presence of an accessor implies read access to all public profiles.

[audsc]

Does adding apublic_profile boolean to the profile make sense to tackle this issue? @Brandogs

[Brandogs]

lets make this field is_private

[audsc]

In our previous access model, from my understanding, all information about access was contained in the KMUserAccessor and ProfileAccessor. Adding this is_private field moves some of that information to the Profile model. Issue #157 further proposes that we remove the ProfileAccessor model, adding an is_admin field to KMUserAccessor. Is this what we want, or is it better to keep access information in separate models?

[cdriehuys]

Since KMUserAccessor holds access information for a specific user, it doesn't make sense for it to contain the private/public state of the profile since that applies to all access.