Refine OpenCV documentation
- Warn if features are only supported with patched OpenCV.
- Clarify what is meant by "in-place"
- In-place is supported for cv:::resize & cv::Sobel because OpenCV will create a new image before calling the HAL.
- Note optimal sigma values for Gaussian blur.
- Note the need to specify accuracy hint for Gaussian blur.
- Add missing constraints on element size for transpose & rotate.
- Fix references to non-existent src & dst parameters.
- Use Mat's type instead of both depth and channels.
- Remove confusing explanation of remap's fixed point format and instead reference OpenCV's docs.
- sum is disabled by default so remove it from the docs.
- ^ means bitwise xor in C, so don't use it to mean power.