Kogneato profile images

[clpetersonucf]

• Adds a new SiteImage model with various image types in support of site-wide images managed through the ORM: PROFILE_IMAGE, CATALOG_BANNER, and eventually LIBRARY_BANNER.
• Adds a new site admin panel visible to super users. The site admin panel supports selection and uploads of images for each SiteImage type.
• Adds a data migration to populate the SiteImage model with a set of default profile images.
• Adds test suite for the site API endpoint.
• Modifies the profile fields metadata to select a profile image at random if the profileImage value is not yet populated. Kogneato portraits are now the default profile image selection instead of Gravatar for new user records.
• Newly instantiated user metadata fields will also select a random profile image.
• Updates the Settings page to include profile image selection if the default value (not Gravatar) is selected.
• Profile settings are now committed immediately through the API (via PATCH instead of PUT) without having to select "Save" at the bottom.

To-dos:

• Ensure fresh instances of Materia properly populate default profile images and profile images are correctly provisioned for new user accounts.