Add Trenz SoM 4x5 footprint

Add Trenz SoM 4x5 footprint

symbol: https://github.com/KiCad/kicad-symbols/pull/1871

Created from https://wiki.trenz-electronic.de/display/PD/4+x+5+SoM+Integration+Guide#id-4x5SoMIntegrationGuide-CarrierBoardChecklist

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All contributions to the kicad library must follow the KiCad library convention

Thanks for creating a pull request to contribute to the KiCad libraries! To speed up integration of your PR, please check the following items:

• Provide a URL to a datasheet for the footprint(s) you are contributing
• An example screenshot image is very helpful
• If there are matching symbol or 3D model pull requests, provide link(s) as appropriate
• Check the output of the Travis automated check scripts - fix any errors as required
• Give a reason behind any intentional library convention rule violation.