Support Double precision type in Scala

[nswamy]

Currently MXNet-Scala APIs support only float32, this would cause accuracy issues when customers port models between developed on Python to Scala. This needs to be fixed

[lupesko]

Thanks for reporting @nswamy - but is this a bug or a feature request?

[nswamy]

This is both a bug and feature request, since the accuracy will drop using Float32 on a model vs Float64

[lanking520]

Let's combine the conversation in here so we can kill dupes in issues: #10338

[piyushghai]

@mxnet-label-bot add [Feature request]