More complete XTrans support

[Alex-Vasile]

Additions for XTrans sensors

• 16bit output support
• Non-linear tone mapping for output
• Exposure bracket burst
• Hotpixel detection and correction

Closes https://github.com/martin-marek/hdr-plus-swift/issues/26.

Special thanks to @gigaturbo and @dejanberic who provided several X-Trans bursts in order to test much of this functionality.