Modify some requirements and language relating to compound schema documents based on feedback in #1032.

Allow embedded schema resources to use relative URIs as opposed to just absolute URIs.
Reference dialect rather than  in terms of processing requirements for embedded resources which don't specify their dialect via .

Author: Relequestual

jsonschema-core.xml

@@ -1856,14 +1856,14 @@
                     <t>
                         The bundling process for creating a Compound Schema Document is defined as taking
                         references (such as "$ref") to an external Schema Resource and embedding the referenced
-                        Schema Resources within the referring document. Bundling is done in such a way that
+                        Schema Resources within the referring document. Bundling SHOULD be done in such a way that
                         all URIs (used for referencing) in the base document and any referenced/embedded
                         documents do not require altering.
                     </t>
                     <t>
-                        Each embedded JSON Schema Resource MUST identify itself with an absolute URI using the "$id" keyword,
+                        Each embedded JSON Schema Resource MUST identify itself with a URI using the "$id" keyword,
                         and SHOULD make use of the "$schema" keyword to identify the dialect it is using, in the root of the
-                        schema resource.
+                        schema resource. It is RECOMMENDED that the URI identifier value of "$id" be an Absolute URI.
                     </t>
                     <t>
                         When the Schema Resource referenced by a by-reference applicator is bundled, the Schema Resource
@@ -1874,7 +1874,7 @@
                         bundling process.
                     </t>
                     <t>
-                        Bundled Schema Resource MUST NOT be bundled by replacing the schema object from which it was
+                        Schema Resources MUST NOT be bundled by replacing the schema object from which it was
                         referenced, or by wrapping the Schema Resource in other applicator keywords.
                     </t>
                     <t>
@@ -1891,14 +1891,13 @@
                 </section>
                 <section title="Differing and Default Dialects">
                     <t>
-                        If multiple schema resources are present in a single document, then
-                        schema resources which do not have a "$schema" keyword in their root
-                        schema object MUST be processed as if "$schema" were present with the
-                        same value as for the immediately enclosing resource.
+                        When multiple schema resources are present in a single document,
+                        schema resources which do not define with which dialect they should be processed
+                        MUST be processed with the same dialect as the enclosing resource.
                     </t>
                     <t>
                         Since any schema that can be referenced can also be embedded, embedded schema resources MAY
-                        specify different "$schema" values from their enclosing resource.
+                        specify different processing dialects using the "$schema" values from their enclosing resource.
                     </t>
                 </section>
                 <section title="Validating">