Create a core interface method to facilitate computed dimensions

[islas]

Currently there is no way of defining a dimension that is derived from preexisting values already present in input data. Various calls in the registry generated code require that state variables that would need a runtime-defined dimension exist prior to their usage and thus prior to the end of the bootstrapping sequence.

As such, it is not feasible to have a core-only implementation of injecting a runtime computed dimension at the appropriate time of setup.

This adds a methodology for cores to provide core-specific computed dimensions implementations by adding:

1. an interface subroutine to the core type
2. a computed dimensions interface types and module
3. invocation of new optional core interface function in bootstrapping

The computed dimensions interface types and modules are based off of the same pattern used for decomposed dimensions.