Power supplu connector - panel isolation

[emmroz]

In regarding to issue #69
I think that it should be proposed a solutoion for SWITCHCRAFT 712RA connector, such as for SMA connentor (issue 69)
For now we added a pressboard washer to isolate the sleeve, hovewer it still could be connection beetween sleeve and the panel due to the too small gap marked in the second photo
As explained by @gkasprow: grounding the power connector bypasses one of the CMC inductors. This may result in lower ground loop impedance and worse EMI susceptibility