Draft Recoil Tracker Geometry for PAC53

[nwuerfel]

Modified from micromegas bmt tracker to the appropriate layer thicknesses and geometry for recoil tracker covering opening angles approx. 40 - 70 deg. The layer structure of the BMT has been preserved, though the support structures have largely been removed for the initial push. Old lingering bits of code refer to bmt, but after everything is approved this can all be updated to correctly refer to RT.

[maureeungaro]

this should be a different micromegas variation, not a separate directory.

[maureeungaro]

let me know if you need any assistance. If you look at the current code you should be able to figure out how to add and use an element to "@custom_variations"