Machine parsable specification

This converts portions of the asciidoc specification into an xml
document and schema. For the html and pdf outputs, the xml is
converted to asciidoc files that are included into the existing
specification.

The xml allows future automated uses of the tosa specification
while maintaining rough compatibility with the existing document.
No significant functional changes are included in this change.

Change-Id: I7f1f95c527638e270c157d58fcdec6a3510daea5
Signed-off-by: Eric Kunze <eric.kunze@arm.com>