[Request] Update navlayers module to support layer file format v4.5

### Describe the solution you'd like
Update the navlayers module to support layer file format version 4.5.

### Additional context
To load a layer file via the navlayers module:
```python
from mitreattack.navlayers import Layer

lay = Layer()
lay.from_file("layer-version-4.5.json")
```
