Add Normative level

Add Normative level to better align w/HL7 ballot levels, also [FMM](http://wiki.hl7.org/index.php?title=FHIR_Maturity_Model)

Author: isaacvetter

docs/hooks/index.md

@@ -157,9 +157,11 @@ Maturity Level | Maturity title | Requirements
 0 | Draft | Hook is defined according to the [hook definition format](#hook-definition-format). 
 1 | Submitted  | _The above, and …_ Hook definition is written up as a github pull request using the [Hook template](hooks/template/) and community feedback is solicited on the [zulip CDS Hooks stream](https://chat.fhir.org/#narrow/stream/17-cds-hooks). (TODO - specify repo that PR should be submitted to).
 2 | Tested | _The above, and …_ The hook has been tested and successfully supports interoperability among at least one CDS client and two independent CDS services using semi-realistic data and scenarios (e.g. at a FHIR Connectathon). The github pull request defining the hook is approved and published.
-3 | Considered |  _The above, and …_ At least 3 distinct organizations recorded ten distinct implementer comments, including at least two CDS clients and three independent CDS services. The hook has been tested at two connectathons.
+3 | Considered |  _The above, and …_ At least 3 distinct organizations recorded ten distinct implementer comments (including a github issue, tracker item, or comment on the hook definition page), including at least two CDS clients and three independent CDS services. The hook has been tested at two connectathons.
 4 | Documented | _The above, and …_ The author agrees that the artifact is sufficiently stable to require implementer consultation for subsequent non-backward compatible changes.  The hook is implemented in the standard CDS Hooks sandbox and multiple prototype projects. The Hook specification SHALL: <ul><ol>Identify a broad set of example contexts in which the hook may be used with a minimum of three, but as many as 8-10.</ol><ol>Clearly differentiate the hook from similar hooks or other standards to help an implementer determine if the hook is correct for their scenario.</ol><ol>Explicitly document example scenarios when the hook should not be used.</ol></ul>
 5 | Mature | _The above, and ..._ The hook has been implemented in production in at least two CDS clients and three independent CDS services. An HL7 working group ballots the hook and the hook has passed HL7 STU ballot.
+6 | Normative | _The above, and ..._ the responsible HL7 working group and the CDS working group agree the material is ready to lock down and the hook has passed HL7 normative ballot
+
 
 ## Changes to the Definition of a Hook (Hook Versioning)