v6.15 - Simplify connection flow for single-user accounts. HubSpot integration fix.

Go straight to "tell your presenter this number" when viewer connects through public link in single-user accounts. This will now be the default for newly-created accounts. For existing single-user accounts, you can turn this on in Account/Configuration/Advanced settings. No effect on accounts with 2 or more users.

Fix for HubSpot integration when not all users have marketplace access.