Added Carbide Nomad modules and program

In the same vein as the Bantam/Othermill stuff, I added support for the Carbide Nomad desktop mill (specifically for PCB milling). I added a "defaults" module that's specific to the machine, including two v-bits that are handy for PCB milling. The effective diameter was calculated using this calculator and I have verified that the values are good, assuming the cut depth is .004 in. I wish the interface was a little more verbose and would convey better that the effective diameter and cut depth are co-dependent. This is what I could do with the UI constraints. I also added a g-code generator module for the Nomad. The only difference from the original that it's based on is that it leaves out two g-codes that are a problem for either the machine or the Carbide Motion CAM software that drives the machine (not sure which). Either way, they are superfluous codes, as is coolant option (which I also removed).

I am in the process of making a 3 part video on (1) how to prepare the right bitmap images for mods (2) using mods to generate g-code (3) milling the PCB on the Carbide Nomad. If this merge request is accepted, I'll use the main mods CE site for the videos. Otherwise, I'll show it with my fork (although I'm not too familiar with GitLab and unsure if it has the equivalent of GitHub Pages)