Dynamic properties clarification

Hi,

Currently we've been in the process of integrating OCIO and believe we've encountered an issue regarding the dynamic properties feature.

As far as we understand, they are solely supposed to be handled by the developers and are not intended to be defined or specified as part of the config as stated in the documentation. However when defining an `ExposureContrastTransform`, should a user fail to set a value for a property such as exposure like so:

```
! {style: linear, contrast: 0.5, gamma: 1.1, pivot: 0.18}
```

The generated processor initialises a dynamic property for the missing exposure value. Given that a config is supposed to be locked this seems to contradict the core intention here, therefore we suspect this is a bug and not intentional.

Could you please clarify whether or not this is intended behaviour. If not no worries, we're happy to assist where we can.

Many Thanks

Beginne mit der Durchsicht der Dokumentation zu dynamischen Eigenschaften und des im Issue gezeigten Verhaltens von ExposureContrastTransform. Ermittle, ob ein fehlender Belichtungswert eine dynamische Eigenschaft initialisieren oder für eine gesperrte Konfiguration abgelehnt werden sollte, und dokumentiere anschließend das beabsichtigte Verhalten oder bestätige den Fehler.

Vom Indexierungsmodell aus dem Issue-Text verfasst.