Document custom models

[robmarkcole]

Add section. Show running with correct logging and link to model store.

~ docker run -v /Users/robin/Data/pytorch-models:/modelstore/detection -e VISION-DETECTION=True -p 80:5000 deepquestai/deepstack:latest
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v1/vision/custom/fire
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v1/vision/custom/licence-plate
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v1/vision/custom/lock
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v1/vision/custom/mask
/v1/vision/detection
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v1/backup
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v1/restore

[EverythingSmartHome]

Hey Robin,

I added PR #213 that should hopefully help with this if you want to check it out, let me know if you want anything else added.