"total weight" adder for weight.tag, by Greg Hanson. Documented in tag.

Similar to 'adder' in shipping.asc, except that it allows you to add
lbs vs dollars to the total weight. There are 3 ways to add

1. Simply add X lbs per cart

[weight tot_adder=1]

Will add 1 lb to total_weight after all other weight calcs.

2. Add X lbs depending on a range of weight

[weight tot_adder.k0_25=2]

Will add 2 lbs to total_weight if weight between 0 and including 25, after all other weight calcs.
(The 'k' is simply a separator.)

3. Add X lbs depending on multiple ranges of weight

[weight tot_adder.k0_3=1
		tot_adder.k3_6=2
		tot_adder.k6_10=3
		tot_adder.k10_16=4
		tot_adder.k16_25=5
	]

Will add 1 lbs to total_weight if weight greater than 0 and including 3, after all other weight calcs.
Will add 2 lbs to total_weight if weight greater than 3 and including 6, after all other weight calcs.
Will add 3 lbs to total_weight if weight greater than 6 and including 10, after all other weight calcs.
Will add 4 lbs to total_weight if weight greater than 10 and including 16, after all other weight calcs.
Will add 5 lbs to total_weight if weight greater than 16 and including 25, after all other weight calcs.