[dev] Merk img patch

[Chuck Hagenbuch]

Quoting Duck <duck at obala.net>:

> - only store image basename since we use only it, not the whole path
> - add parameter Merk_Driver_sql::getItemArray() to load image data only if
> needed (needed only while editing)
> - don't need subcategories since we already render the whole tree

Committed, thanks!

-chuck

-- 
"we are plastered to the windshield of the bus that is time." - Chris