Validate input data before training the models

[barjin]

As mentioned in #339 (and the related comments), the collected input data can contain arbitrary values (e.g. as a result of a penetration test run against the collecting server). This leads to the generation of less believable (or even potentially dangerous) fingerprints.

The input data should be validated before training the models with generator-networks-creator to ensure we only generate real fingerprints. This could be simple for some properties (e.g. Navigator.appCodeName should be always Mozilla), but may be impossible for other properties (e.g. Navigator.userAgent can be pretty much arbitrary string - sans the syntax).

Note that this blocks re-enabling the automatic updates of the models.