Editorial cleanups
fixing spec bug
Proposed refactoring to achieve better alignment on JSON-LD:

1. Remove Natural Language Value. Add displayNameMap, titleMap,
summaryMap and contentMap to JSON-LD @context definition, discuss
JSON-LD default language context and rules for value objects

2. Refactor as:Link. Add as:href to link. Make as:Link disjoint from
as:Object. Explicitly define as:Link as a qualified relationship. Add
height, width, duration to as:Link

3. Various documentation cleanups
Continued proposed refactoring

* Deprecate verb in AS 2.0 in favor of @type approach
* Start providing clearer AS 1.0 to AS 2.0 processing rules
* New AS1->AS2 specific JSON-LD @context
* Strengthen extension MUST IGNORE language, mention JSON constructs
that cannot be used within JSON-LD, provide examples for the known
GeoJSON incompatibility,
* Adding in the application/stream+json media type registration (this
was never formally registered before)
Remove the Verb and ObjectType classes from the vocabulary.
include a summary of changes
few tweaks to clarify examples and language around links
Updates to the vocabulary definition
Move the ontology definitions to a separate jsonld document.. add
convenience definitions for other terms so that they can be interpreted
properly.
remove extra spaces
fixing some context def bugs
Add ed notes around the changes made
Merge pull request #55 from jasnell/refactor2

Merging proposed changes into master for review