v1.4.0 Group stats, other major improvements

Biggest addition is the group stats. You can now select entire groups of items and see various stats that I thought were relevant for trading, including volume, ROI, historical trends, and margins.

Also added a slider for price history. Due to excel limitations it's very jank, but it works well for what it is.

At this point, the sheet is a lot more expansive than what I had in mind when I first started this. Not sure where it's going to go, but we'll see. Also not going to bother with sheet/cell protection; if you're using the sheet you're probably smart enough to know what you're doing anyways.