Change how we link to type definitions inside the spec

[luksa]

I suggest we change the way we link to the definitions of OSBAPI types in the spec.

For example, let's take the row that shows the "schemas" field in https://github.com/openservicebrokerapi/servicebroker/blob/v2.13/spec.md#plan-object.

I suggest we replace the word "object" in the second column with the following text: "Schema object". As shown here, the name of the type links to the description of said type.

Similarly, the second column in the "plans" row under Service Objects would be "array of Plan objects" or simply "[]Plan" instead of "array-of-objects" as we have now.

[luksa]

Something along the lines of: https://github.com/luksa/servicebroker/blob/9620a17665768dcde2f4d6a426d7d7eea2f6f9a1/spec.md#plan-object

[duglin]

@luksa want to open a PR so people can see the proposed edits in context? ok if I assign this and #450 to you?

[luksa]

Closing (fixed by #459)