Re-order CDDL definitions so that Command / Message are first (#83)

The first rule in a CDDL document defines the entry point to validate a CBOR
data item. The CDDL of each module started with `Extensible`, which essentially
made any CBOR data item valid.

This update makes `Command` and `Message` the first CDDL rules in each module
(as done in WebDriver BiDi), and defines `Extensible` is a single block common
to both the remote end and local end definitions.

index.bs

@@ -121,10 +121,6 @@ This section gives the initial contents of the remote end definition and local e
 [=Remote end definition=]
 
 <xmp class="cddl remote-cddl">
-Extensible = {
-  *text => any
-}
-
 Command = {
   id: uint,
   CommandData,
@@ -143,10 +139,6 @@ EmptyParams = { Extensible }
 [=Local end definition=]:
 
 <xmp class="cddl local-cddl">
-Extensible = {
-  *text => any
-}
-
 Message = (
   CommandResponse //
   ErrorResponse //
@@ -185,6 +177,14 @@ EventData = (
 )
 </xmp>
 
+[=Remote end definition=] and [=local end definition=]:
+
+<xmp class="cddl remote-cddl local-cddl">
+Extensible = {
+  *text => any
+}
+</xmp>
+
 Capabilities {#protocol-capabilities}
 -------------------------------------
 

schemas/at-driver-local.cddl

@@ -1,7 +1,3 @@
-Extensible = {
-  *text => any
-}
-
 Message = (
   CommandResponse //
   ErrorResponse //
@@ -39,6 +35,10 @@ EventData = (
   InteractionEvent
 )
 
+Extensible = {
+  *text => any
+}
+
 SessionResult = (SessionNewResult)
 
 CapabilitiesRequest = {

schemas/at-driver-remote.cddl

@@ -1,7 +1,3 @@
-Extensible = {
-  *text => any
-}
-
 Command = {
   id: uint,
   CommandData,
@@ -16,6 +12,10 @@ CommandData = (
 
 EmptyParams = { Extensible }
 
+Extensible = {
+  *text => any
+}
+
 SessionCommand = (SessionNewCommand)
 
 CapabilitiesRequest = {