[ZDP] new ZDP project: tag reference list.

[Anthony Baxter]

Would someone like to set up a list of all known <!--#tags --> on a web
page, then we can start filling them in, adding entries for all the options
they take, when they're applicable, &c.

Yes, most of them are already documented, but they're scattered throughout
the docs.

Let's see how I go with naming them all:
Standard ones:
var
call
with /with
in [else] /in
if [else] /if
comment /comment

Aqueduct adds:
sqlvar
sqltest
sqlgroup /sqlgroup
and /and
or /or

Any I missed?

Anthony.