Customizable Temperature Tower

(See "Change History" near the bottom of the page for information on recent changes.)

I've been experimenting with a lot of new filaments, and you know what that means -- it's time for a temperature tower.

I found a number of good towers, especially quirxi's https://www.thingiverse.com/thing:2615842 , but they all seemed to have a few problems:
* The temperature markings on the tower sometimes don't line up with the instructions for how to modify the gcode to add the actual temperature changes, producing inaccurate results. For example, many towers have a base, which is nice. But that base can throw off the height calculations. If you modify the gcode to change the temperature at 10mm, 20mm, 30mm, and so on, but the base means that the tower stories actually start at 12mm, 22mm, 32mm, and so on, then the bottom 2mm of most stories is going to get printed with the wrong temperature.
* Most towers only have a single bridge printed in each temperature, which isn't always helpful.