Tests for "Determine Default Types" section

[jstoiko]

This part of the tests needs to be reworked a bit:

• [ ] some tests are in /raml-1.0/spec-examples/APIs/, they should all be inside /Types/determine-default-types/
• [ ] we need to add a few more invalid tests, see below

Common misconceptions (see the Determine Default Types section of the RAML 1.0 Spec):

• items determines default type to type: array, this is wrong.

  (...)
  types:
  Foo:
  items: string # invalid, missing `type: array`

• fileTypes determines default type to type: file, this is also wrong
• there might be others based on type-specific facets, let's go over the other types and add more test cases if necessary