Add Server Support for Lookup Resource and String Enumerations

[darnjo]

In order to support string enumerations in the RESO Web API, the server must support the Lookup Resource.

• Required Annotations
  For each enumerated field, there is a required annotation in this case for Data Dictionary 1.7. This will be changing in the future, where the Field Resource will be able to advertise these values instead, but we need to write it into the OData XML Metadata for now.

The required annotations can be found in the DD 1.7 specification.

Each single- and multi- valued field will need those annotations.

There will have to be some logic to detect whether a given field is a lookup field or not (if there's not already) and then emit the annotations for those field.

• Required Data Types
  Currently, the reference server assumes OData Edm.EnumType enumerations. To support string enumerations, single- and multi-valued lookups will become Edm.String and Collection(Edm.String).

Since the underlying fields become strings, there is no longer a requirement to build the enumerations into the OData XML Metadata as part of the server instantiation process.