BUGFIX: make sure customer window js variable is defined
Merge identical items during receipt filtering instead of during
receipt sorting. Only merge same-price items. Rewrite trans_id
on member special lines to place them near the applicable item.
Reset "End" variable on manual subtotal. Clears any oddities related
to ending previous transaction.
BUGFIX: when writing ini.php, quote numeric values that start with
zero (and are not literally just 0)