Clean up "actor" vs. "agent/group" usage in statement querying

* Remove "Statement Object (JSON)" from type, no related information in
  "description" column
Put back "(JSON)" in type column for statement querying
tiny typo
rewrite of 4.1.2 Actor

plus some changes to identified group property table
forgot change two words
and a typo...
Merge pull request #82 from brianjmiller/master

Correct Actor/Agent usage
Merge branch 'master' of https://github.com/adlnet/xAPI-Spec
Updated rewrite of 4.1.2 Actor

based on Andrew's and Russel's review comments. Thanks.
* Renamed sha-2 and content-Type properties to sha2 and contentType for easier reference as properties
(many languages don't like - in property names)

* Added clarifying requirements
* Added requirement to include hash in each part's header, so receiver doesn't
have to guess which hash length to use when verifying

* Added an example
minor clarification:
"only send one copy" language only applies within a single message
Added flag to include/exclude attachments when retreiving statements
(trivial) updated example hash

Hash in the example was calculated improperly, updated with correct hash.
Removed 'authoritative' flag

Shouldn't be controversial, I think we talked about removing this in 0.95 but just forgot to.

For those new to the discussion: this is a holdover from when the LRS was "smarter" than it is now -- we've decided it's up to systems reading statement to decide how to weigh statements.
Merge pull request #86 from paul-esch/master

Rewrite of 4.1.2 Actor
Merge pull request #88 from bscSCORM/nonauthoritative

Removed 'authoritative' flag
Merge pull request #87 from bscSCORM/binary

Attachment example, clarifications, minor changes
Merge pull request #13 from adlnet/master

update adlnet master to garemoko