Hierarchical Priors on Core Module

[andresmasegosa]

Functionalities to deal with Hierarchical Priors (when a parameter variable or non-replicated node has parents) are now included for the core-module in this branch. Tests are passed but no hierarchical prior concrete example is introduced.

[steveash]

Any ETA on the example? I am trying to build a hierarchical model with multinomial variables with dirachlet priors and would love an example