Add tests to cover RAML v1.0.1 patch

[jstoiko]

In preparation of the RAML v1.0.1 patch release, we need to make sure TCK tests are updated to reflect the clarifications.

[postatum]

• [x] Clarify how to resolve !includes and libraries inside Overlay and Extension fragments
• [x] Clarify that libraries may be used in any type of fragment
• [x] Clarify requirement level of the pattern facet for type string
• [x] Clarify usage of enum in a union type
• [x] Clarify use of type-specific facets in a union type
• [x] Clarify how to infer/determine the default type for ALL built-in types
• [x] Clarify formatting of examples
• [x] Clarify nilable property alternative syntax
• [x] Clarify that references to inner elements only apply to JSON Schema / XSD
• [x] Specify that RAML documents MUST be valid YAML 1.2 documents: Nothing to add here.
• [x] Clarify that value of is in Applying Traits MUST be array

Wontfix:

• Clarify use of trailing question mark: Already covered by existing tests.
• Make all examples use / instead of /: No tests to add here. It's just a change of wording.
• Issue with second "Introduction" link in RAML 1.0 table of contents: Nothing to test here.
• Clarify "NamedExample" typed fragment description and usage: Already covered in tests/raml-1.0/Fragments/
• Add missing "format" facet in Date type: Already covered by existing tests.

[jstoiko]

Specify that RAML documents MUST be valid YAML 1.2 documents: Nothing to add here.

how about adding one or more tests with YAML 1.2 -specific syntax?

[postatum]

Specify that RAML documents MUST be valid YAML 1.2 documents: Nothing to add here.

how about adding one or more tests with YAML 1.2 -specific syntax?

Added.

[jstoiko]

Good. Let's move the YAML 1.2 line above out of Wontfix...

[postatum]

Good. Let's move the YAML 1.2 line above out of Wontfix...

Done