Move logical field type determination down to the model

The form may not be the only place the "logical type" could be used.
This also lays the foundation for allowing upstream components to set
the logical type of the field (e.g. Serrano or Avocado).

A field's logical type can be used to drive it's behavior in Cilantro.
Add granular configuration options for concepts and fields

For details, read the documentation in the cilantro.config module.

Fix #390
Merge pull request #401 from cbmi/issue-390

Add configuration options for concepts and fields