Adds TGA 2.0 compliance:
- Support for Extension Area, Developer Area and Footer (metadata support)
- Support for 15-bit and 16-bit per pixel images (both RGB and Indexed)
- Full support for rotation on reading (we cannot use Qt transformations because only a subset is part of the TGA specification)
- When writing you can choose the supported version (subType)
- Improved writing speed (approximately 10 times) and removed whole image conversions (significant memory savings)
It pass the [TrueVision TGA 2.0 conformance suite](https://github.com/zigimg/test-suite/tree/master/fixtures/tga).
Test changes:
- Read test: added ability to skip a specific test on sequential devices (via JSON behavior file)
- Write test: added the ability to set the subType when writing (via JSON properties file)
Closes#37
- Removed temporary buffer of uncompressed image size when reading (loads images using half the memory)
- Added native support for Grayscale images (they are no longer converted to RGB(A) 32 when reading/writing)
- Fixes wrong X channel value on RGBX32 images (CCBUG: 499584)
It should also reduce loading times for corrupted images.
Closes#33
Closes#11
Requires MR !279
On formats that does not support CMYK and does not use the ScanLineConverter class during write operation, the CMYK images must be converted using the color space conversion functions of `QImage` (if ICC profile is valid).
