FR7 Straight Arm Edition

This is a slight modification to the FR7 open source FPV frame design to straighten out the arms in the dead cat configuration. This adds minor structural and aesthetic benefits.

*Updates May 31st: Options options options!
- "no_slots" files remove the slots for holding underslung batteries
- "through_hole" components use 6mm oversized inner holes so that the FC stack only attaches to the rear plate, without the bolts touching the arms or front plate. This is the same as the FR7 V4x. Note