cmake: introduce setup_vars scripts

typo in kmeans doc

* avoid rounding errors

* imgproc: replace condition in matchTemplate

ffmpeg 3.4.2 -> 3.4.5

During the cluster-based detection of circle grids, the detected circle
pattern has to be mapped to 3D-points. When doing this the width (i.e.
more circles) and height (i.e. less circles) of the pattern need to
be identified in image coordinates.

Until now this was done by assuming that the shorter side in image
coordinates (length in pixels) corresponds to the height in 3D.
This assumption does not hold if we look at the pattern from
a perspective where the projection of the width is shorter
than the projection of the height. This in turn lead to misdetections in
although the circle pattern was clearly visible.

Instead count how many circles have been detected along two edges of the
projected quadrangle and use the one with more circles as width and the
one with less as height.

- CMake install COMPONENT: "scripts"

* Fix reading of black-and-white (thresholded) TIFF images

I recently updated my local OpenCV version to 3.4.3 and found out that
I could not read my TIFF images related to my project. After debugging I
found out that there has been some static analysis fixes made
that accidentally have broken reading those black-and-white TIFF images.

Commit hash in which reading of mentioned TIFF images has been broken:
cbb1e867

Basically the fix is to revert back to the same functionality that has been there before,
when black-and-white images are read bpp (bitspersample) is 1.
Without the case 1: this TiffDecoder::readHeader() function always return false.

* Added type and default error message

* Added stdexcept include

* Use CV_Error instead of throw std::runtime_error

* imgcodecs(test): add TIFF B/W decoding tests

* Update imgproc.hpp

* update color conversion codes