Update default user profiles to use Kogneato portrait gallery

[clpetersonucf]

The idea:

• Set the default user profile image to the Kogneato portraits being developed
• Create a new Kogneato profile picture image gallery for users to select from
• Gravatar integration remains but is no longer the default

This would require one significant UI addition: the portrait gallery, which could conceivably be another tab from the profile + settings UI, or a modal launched from the user settings page.