Hdrutils

Additions:
- Programmatically capture images with *gphoto2* by connecting a DSLR
- Improved exposure estimation with MST-reduction and Tikhonov penalty; quicker method agnostic to resolution
- Merge returns an unsaturated mask for post-processing without color artifacts

- Includes exposure estimation of Cerman and Hlavac
- Better scatter plots to check linearity
- Iterative outlier removal for robust exposure estimation
- Align RAW bayer images

- Updated noise simulation interface
- Automatic exposure estimation to account or illumination changes
- Added tests for common functions

Additional functionalities:

- Simulate calibrated cameras using simple noise models
- Write FP16 HDR images
- Merge non-demosaiced PNG images

This update has the following additions and fixes:
- Merge before demosaicing mode now supports more colorspaces (sRGB, Adobe)
- Feature matching for homography done on scaled images
- Better logs and warnings for alignment

Summary of changes:
- Better 16-bit png support
- Clip negative pixels after HDR merging
- Improved logs
- Continue merging even with failed alignment