Add SMA_Samtec_SMA-J-P-H-ST-EM1_EdgeMount model

[bitglue]

Work is my own, done with FreeCAD, based on the mechanical drawing at
http://suddendocs.samtec.com/prints/sma-j-p-x-st-em1-mkt.pdf

Some of the dimensions aren't specified in the drawing so I guessed. I
don't have this particular connector but a very similar one so I wasn't
able to measure.

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[CLAassistant]

All committers have signed the CLA.

[bitglue]

I guess "Geometry check performed on the model" means Part -> Check Geometry in FreeCAD? If so, did that. If not, please link instructions and I'll be glad to do.

[bitglue]

A couple shortcomings I know of:

• the geometry of the threads is not exactly right. I'm no mechanical engineer and researching exactly what the geometry should be seemed like too much work.
• chamfers and a few similar details are omitted. I figured they'd just slow down rendering.
• it looks like this connector is designed for an interference fit: the center pin protrudes down a little lower than the legs that sit on top of the board. I also wasn't sure exactly what board thickness to expect, so the Z axis positioning is just eyeballed.

[bitglue]

@aris-kimi if you wouldn't mind reviewing this model also