Instance customization

[MarkWieczorek]

Allow administrators to customize certain elements of their instance from the GUI. All customization options should have a default hard-coded value in the .env file.

Proposal:

• Create a menu item "Customize" that is visible to site administrators (role_id=3).
• Add customization options to a new database table. This table should be initialized using default values from the .env file.

Customization options:

• Header background and font color.
• Footer background and font color.
• Main text background and font color.
• Title and subtitle used in the header of the home page (action_name, action_short_description and action_kind)
• Text for the home page.
• Option to show/hide example petitions on home page (show_examples)
• Option to thank PRC (thank_prc)
• footer_url_name
• footer_url
• Option to allow all users with ORCIDs to have editor permissions (everyone_is_editor)

Note: Given that the database will be updated to include a new table of customization options, it will be necessary to provide a mechanism to update any pre-existing databases.