Refactor instance, binds, submission

Refactor instance, binds, submission so that they can be used interchangeably.

For example, it seems that we need a bundle called instance. It needs a referencing system, a data format, a notion of readonly, and the (insert, delete, setvalue, getvalue) bundle.

Need a separate module that could define model item properties for the data, perhaps without describing a method for calculating them. Just getters and setters.

Yet another module could offer dynamic control of the MIPs. One instance of that might be a system that uses the referencing engine to set up declarative formulae.

The submission module should only need the generic instance object. It should be able to consume MIPs like relevance and validity if available.