Define format for firmware update package

[malczuuu]

Let's have some defined format of package images (either uploaded via /5/0/0 Package or pulled via /5/0/1 Package URI). Therefore, this emulator would be able to do some validation of the package.

This could be a simple YAML or .properties file.

[malczuuu]

It could work like that:

• file format is a JSON, with following schema

  {
    "version": "1.0.0",
    "color": "blue"
  }

• after firmware update, backfround of the FE application changes collor to the requested one