Solr schema should support DocValues

[cjcolvar]

Copied over from samvera/hydra-head#395 since the solr config no longer lives in hydra-head:

This is yet another dimension of the sprawling matrix of attributes responsible for defining dynamic namespaces, but it is important. DocValues enables the use of Streaming Expressions via the /stream handler.

The good news is it only affects StrField, UUIDField, Trie* numeric/date fields, and BoolField. The bad news is that I don't think our strategy of enumeration is sustainable as other attributes (and attributes with wider range of values) proliferate.