* persistence: replace arbitrary limit of cn to 4 by CV_CN_MAX

* python: added persistence test, remove temp files

* fixup! python: added persistence test, remove temp files

* fixup! python: added persistence test, remove temp files

Implementation of bit-exact resize. Internal calls to linear resize updated to use bit-exact version. (#9468)

Tests are usually lauched from source directory, so additional unnecessary
files should be eliminated.

Alternative ways (command line):
- python -B ...
- PYTHONDONTWRITEBYTECODE=1 python ...

Usage example (bash):
$ OPENCV_PYTEST_FILTER=test_digits python test.py -v

Original commit is a5f19f7dd6ae5bc93f73e0417a9e0bfd34c01672

- fixed uninitialized memory access and memory leaks
- extracted several code blocks to separate functions
- updated part of algorithm to use cv::Mat instead of CvMat and IplImage

1. if a component's variation is a global minimum than it should be a local minimum
2. for the small image with invert and blur, the MSERs number should be 20

Test launch script updated to run new tests as well.