Fix support for list copy

Fix attribute to list copy

Remove not yet valid assertion

Don't allocate VALUE_PAIRs just to free them later

Fixes #353
Sprinkle vp->type = VT_DATA in more places, this will be needed later
Simplify paircopy functions and fix them so they can't return half copied lists
Fix all the update list debug output

Make list output more detailed

Consistently use single quotes for literal strings, only use double quotes around things being expanded

Replace delimitst with quote char, to allow caller to pass any quoting char