Create a new ReSpec section for references

In order to be consistent with OASIS specification templates, references should be generated right after Terminology and before Typographical Conventions in the Introduction section:
1 Introduction
1.1 Terminology
1.2 References - Normative and Non-Normative References
1.3 Typographical Conventions - what is currently called "Conformance"

To support this, ReSpec should be updated with a new <section id='references'> so that editors can control where the references section is generated.