Bug 2919 -- fix value_builder plugins for dateaccessioned, barcode

Bug 2919 -- fix value_builder plugins for dateaccessioned, barcode

This patch depends on my previous one "Begin cleanup on additem" and
fixes one bug introduced in that patch.

Overhaul of additem sections to factor out common pieces especially attributes.
Plugin js vastly simplified and reimplemented in jquery.  Performance improved.

Note that a particularly busy cataloging department should still leave
barcode blank for server-side autopopulation to avoid collision.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>