Freezing of the factory

[kitsonk]

Originally, I thought it was wise to freeze the returned factory, basically to keep factories immutable, and limit the amount unanticipated consequences. The challenge is that it makes it impossible to add static methods/properties to the factory.

There are three approaches I can see to resolving this:

• Don't recommend/support static properties or methods. If the default export of a module is a factory, it is "better" from a potential code optimisations mechanism, to export static methods related to the factory as part of the module. Of course, this may not gracefully handle typing with downstream composites.
• Don't freeze the factories
• Add an API to allowing the addition of static properties. The challenge will how to handle the type inference to return an extension of the ComposeFactory. Likely we would need TS 1.8 with F bound polymorphism (see: Type parameters as constraints microsoft/TypeScript#5949).

If we choose either of the last two, we will have to change the factory cloning logic to perpetuate these static method/properties, which it currently does not do.

[kitsonk]

@maier49 has implemented as much of a level of freezing as we have felt safe but still workable.