Implement toggling between organizations

[chriscarrollsmith]

• Add a dropdown (at the top of the dashboard?) so the user can toggle between their organizations
• Persist the selection with a cookie
• Use the selection to control which organization's resources are displayed on the page

To illustrate this behavior in the template, maybe we seed the database with a sample user and a sample Promptly Technologies organization, and we have some Promptly Technologies-specific data asset load on the main page only if that organization is selected in the dropdown. There should also be some text like "Organization-specific assets will display here:" that is always visible regardless of the selected organizations.