Use smarter defaults in type specification

[andylowry]

It's pretty annoying to constantly have to write stuff like this in the types specification:

    description:
       name: Description
       type: String

The property key above is the field's id value, and is the default for it path within its containing object. The name should also have an intelligent default based on the id, and settling on String as the default would make things additionally concise.

For name default, the following rules will apply:

• Only the final component of the id value will be considered (where components are separated by slash characters). E.g. with components/schemas only schemas will be considered when determining the default name.

• If the field is a scalar, or if the id value does not end in s, then the last component of the id, with its first character upper-cased, is the default name.

• Otherwise (collection or map field, and id ends in s), the last component of the id, with the first character upper-cased and the final s removed, is the default name.

[andylowry]

Implemented in #125

[andylowry]

As described in #125, defaulting a missing type to "String" was altered to retain existing default behavior (which I had forgotten about). Rules for a missing field type are now:

• If the field name is the name of a type defined in the type config, that type is used for the field
• Otherwise, String is used.