Remove -- from doc-files.

Thanks to Andreas for pointing this out.

Delete trailing whitespace in help/Docfiles

update SUBST Docfile for recent change to its implementation

Huge number of check-ins, implementing change to .doc file syntax.
Now the rule for text within braces is that it appears as given, but
that braces must balance. If you want an unbalanced brace, you can use
\lbrace or \rbrace. No existing .doc file uses unbalanced braces.
Also, there is now no need to use \noindent. In fact, doing so
will get you a complaint from the parser. Similarly, use of \ or
{} characters outside of verbatim text blocks will cause griping.
All of the new files have been generated by a parse-then-print process
from the old files, and it's possible there are errors. If you ever
have a spare moment, casting your eye over a random selection of these
might help to find errors.

New docs, especially for the DB structure. Also some editing
of previously-written stuff.

Tag and Thm are documented. Plus fixes to existing docs.

New versions of docfiles.