[support] Sub-theme

[Roger]

<snip>
So, either the database must be updated somewhere, somehow, by someone, 
-- OR -- Drupal must look at the filesystem and realize that there is 
more to the story than the database knows and extend the list. So, how 
does Drupal become aware of the custom sub-theme?
</snip>

I'm lost as to why you want to do this, because what you want doesn't 
make sense but here goes:

Drupal default core reads core themes, if theme not found reads 
/sites/default/themes/

Ok here's what I did just now!.
Created /sites/all/themes/Bartik_cfm folder. Underscore not hyphen, 
explained below!
Copied bartik.info over to this folder, renamed it Bartik_cfm.info

Copied stylesheets[all][] = css/layout.css to the Bartik_cfm/css and 
renamed to stylesheets[all][] = css/local.css

Deleted everything in the .info file except:

  name = Bartik_cfm
description = Yadda Yadda Yadda stuff about the copy.
package = Core
version = VERSION
core = 7.x

stylesheets[all][] = css/local.css

version = "7.23"
project = "drupal"
datestamp = "1375928238"

Notes:
-- If the Theme name has a hyphen it will not work - It seems to require 
an underscore.
-- Underscore is a recognised variable name separator in php, ruby and 
other languages, hyphen can be interpreted as a minus sign. Avoid 
hyphens in names and terms.
-- The last 3 lines are required in the info file or it won't work (for 
me). Don't know why!

Hope this helps
Roger