changed about/version to an array

In order to leave the door open for a future LRS that supports 1.x.x as well as 2.x.x, but without a 2.x.x specification __requiring__ 1.x.x support, making the about/version property an array so that an LRS may list the versions it supports.
[] -> Array, xApi -> xAPI

In response to feedback:
* changed string[] to Array of string
* changed xApi to xAPI
Merge pull request #3 from adlnet/master

Sync up!
Section 4.0 - 4.1.2.3 Edits

Generally, all sections within 4.0 should be rewritten to have a particular order to them.  Description should be first, and be text only.  If Rationale is needed, it would follow. The Details section should have any Testing Requirements as bullet points that can stand alone.  The Details sections should have the Properties tables as well. Some Details sections end up with sub-sections of their own, and will have different labels.  Eliminated "flavors" of objects within type field in tables i.e. account object.

Functional change - the MUST NOT instead of SHOULD NOT for IFIs used as Group ids and vice versa - can anyone shed light on how the two could co-exist to justify the SHOULD?
about version

Updated about version to allow indicating support for future and prior versions
fixed typo in voided URI
Merge pull request #225 from bscSCORM/voided

fixed typo in voided URI
Reverted Agent/Group id req back to SHOULD NOT
Merge pull request #223 from andyjohnson/master

Section 4.0 - 4.1.2.3 Edits
Merge pull request #213 from bscSCORM/about

changed about/version to an array