Save values when parsing attribute value.

Needed in case there's any nested uses of values.
Validate and process link values.
Allow template calls in anchors, roles and includes.

Actually a subtle change, as includes and anchors could previously
contain spaces. Possibly should still alow that, although I expect it's
never used.
Update 1.7 note about attribute templates.
Inline element id version checks.
Use quickbook 1.7's attribute value for element ids.

Allows use of templates, and allows more characters, ids now end with
whitespace - like ids in links.