note in docs how to reference drizzle schema

[rizen]

Specifically, talk about VingKind.table being a reference to drizzle schema, and then getting field definitions from there.

[perlDreamer]

I think this example on how to manually update a User needs to mention .table, too:

https://plainblack.github.io/ving/subsystems/ving-record.html#update

[rizen]

added