Implement JSON-LD context use cases

[warriordog]

Implement following low-level use cases:

• IReadJsonLDContext - deserializes a context from a string.
  • Additionally, add extension methods to read from an embedded resource.
• IWriteJsonLDContext - serializes a context into a string.
• IGetJsonLDContext - wraps IReadJsonLDContext with cache logic.
  • Create options class to select cache implementation(s)
  • Create cache service IJsonLDContextCache - caches JsonLDContext and JsonLDContextObject classes.
  • Create options class to configure cache invalidation

Final call graph will look like this:

IGetJsonLDContext -> IReadJsonLDContext
                  -> IJsonLDContextCache

IWriteJsonLDContext

[warriordog]

nevermind, this is really not that useful.