On-boarding flow & UX cleanup

Immers Server

• Allow deep navigation direct to registration panel in login view
• Fix login/profile layout on mobile devices
• Fix difficult handle entry on mobile keyboards

Hubs Client

• Clean up scene entry / on boarding flow
• Remove many UX prompts that require hubs account registration if not already logged in (e.g. create avatar, create scene, favorite room, pin item)
• Fix loading custom avatar from URL
• Fix hubs disconnecting in background while going through registration form