Fix connection URLs to work with RBAC

"Start Using SDK" and throughout ALL Documentation, the RBAC related connection method and URLs must be updated.  Marked as Blocker as without these instructions all users of 5.0 related builds (from April onward) will have errors connecting and not know next steps.

1. Update URL and authentication method for passing with user, bucket and (no longer optional) password
2. Note change to using 'default' bucket, since it does not exist in the 5.0 version and beyond, so cannot be assumed to exist

Reference:

• RFC documents SDK approach
• Adding RBAC support to SDK