Export the extracted PlatinaFacts to PML

The facts are exported to the modelfacts member in the PML-files.
Syntax is as follows:

```YAML
modelfacts:
  - program-point:
      function:        c_entry
      block:           if.else
    origin:          platina.bc
    level:           bitcode
    type:            guard
    expression:      'false'
```