Bringing default editor closer in line with WEFC

I added a field for the longer description in the same
place as WEFC.

I put the "Last modified" date where WEFC has vendor SKU mostly
to make use of that space. I don't think a single SKU field is
workable. The VendorItem module does provide SKU and cost fields.
It just provides more of them with a separate set for each vendor.

I move recent & price history links into the horizontal row with the
submit button, "Back" link, etc. It fits well enough and makes the
entire Operations/Links field set unnecessary. I got rid of the
current vs. new shelf tag distinction and put a "Shelf Tag" link on
both the editing page and the little summary that appears after saving
an item. It covers both options in a way that takes less screen space
and gives the user an additional chance to remember they need a tag.

I added the VolumePricing module to emulate WEFC's "Three for a dollar"
fields. It's mostly the same but I made "method" a dropdown rather
than a number. Seems more intuitive to me.

The main things I see remaining are the "sale" fields and some kind
of option to rearrange / re-flow the modules' display order.
I think the sale editing should be disabled by default configuration
with batches as the recommended practice, but we can still support
the option of direct editing. As far as layout goes, I prefer mine :D.
WEFC's is more space efficient, but either way you have to scroll. I think
the uniform width looks better than the variable height (and yes, I do
realize membership uses the latter; that might be have been a poor choice
on my part). Re-ordering the modules will be a necessity either way.