Multi format output

[julioz]

Currently, FloorPlan only allows for outputting one format at a time.
We want to enable multi format output, so that users can mix-and-match renderings as they seem fit.

The gradle plugin interface will then allow for multiple output enablement:

floorPlan {
  schemaLocation = ...
  outputLocation = ...
  outputFormat {
    dbml {
      enabled = true
    }
    svg {
      enabled = true
    }
  }
}

The CLI interface needs to also be rethought, to extend the --format argument to receive a List instead of a String. The curious bit is how we can make "nested arguments", given DBML can receive its own sub-parameters for rendering.