Support for referring to data types via their constructors

[srid]

This,

data Query t r where
  Query_Foo :: Query String Int

deriveJSONGADT 'Query_Foo

gives:

tyConArity': Supplied name reified to something other than a data declaration: Neuron.Zettelkasten.Query.Type.Query_Foo

[cgibbard]

We should make the task done by tyConArity' use th-abstraction instead, which is important to make this code write instances for data families.

[cgibbard]

see also, #24