Default "submissionSchema" to true

Now that we have "targetHints" which, among other things, can
provide information about which HTTP methods are supported, there
is no longer a clear need to prevent submission by default.

It is more in line with the rest of JSON Schema's philosophy to
allow unconstrained input by default.

Note that "hrefSchema" remains false by default due to its
interaction with resolving URI Templates from instance data.

Author: handrews

jsonschema-hyperschema.xml

@@ -907,20 +907,7 @@
                             representation.
                         </t>
                         <t>
-                            Omitting "submissionSchema" or setting the entire schema to "false"
-                            prevents any user agent data from being accepted.
-                            <cref>
-                                Is this correct?  In draft-06 this was the only way to signal
-                                support for data submission, but now we have "targetHints" for
-                                that.  It may make more sense for this to default to behaving
-                                as if the schema is set to true.  The original idea was that
-                                both this keyword and "hrefSchema" indicated the presence
-                                of optional functionality.  This makes sense for "hrefSchema",
-                                as it is used with "href" which is owned by the hyper-schema.
-                                However, "submissionSchema" describes a message that is
-                                supposedly accepted by the target resource.  In general, we
-                                choose defaults that avoid constraining target behavior.
-                            </cref>
+                            Omitting "submissionSchema" has the same behavior as a value of "true".
                         </t>
                     </section>
                 </section>