Convenience API to set an instance

[jkrems]

We keep running into places where we have code like this:

registry.singleton.setFactory('simpleStaticThing', null, () => simpleStaticThing);

This can now be written as:

registry.singleton.setValue('simpleStaticThing', simpleStaticThing);

[dbushong]

that always seemed kind of silly

[jkrems]

Other common ones are setClass etc. but I don't think we actually have use cases for them.