Replace radial menu with boxy edit menu

After much frustration with the radial menu, I decided to take a shot at #1994 - Radial Menu gets in the way.

I changed the menu to be a more tightly packed box.  This is nice because it tends to avoid nearby points, and we can add many more operations to the menu without it becoming too unwieldy.

I also added the ability to control which direction the menu pops up.  The calling code in select.js could check for nearby points on the selected entity, and tell the edit menu to avoid them, although I haven't implemented this yet.

![editmenu](https://f.cloud.github.com/assets/38784/2306713/34f3b026-a292-11e3-89db-7913ba4fe7f0.png)
(In this screenshot I added extra dummy "delete" operations to test column packing code and show what a larger menu would look like).