Theme and/or branding

**Is your feature request related to a problem? Please describe.**

The documentation doesn't indicate any ways to inject custom branding, colour pallet or override the content on the default page when you access a RES deployment.

**Describe the solution you'd like**

The ability to brand the solution to our wider project as it is a multi organisation solution and clearly indicating the "host" organisation builds confidence.

Use a DynamoDB table to allow override of the following:

* URL for Logo & favicon
* primary & secondary colours (or wider definition as required)
* Banner text on landing page
* Content of primary panel on landing page
* Disable other panels on landing page

**Describe alternatives you've considered**

Manually updating the source code requires wider skill sets and has support overheads.

**Additional context**

OGVA based support contract in place, large public funded project.