- don't use RNG for "task size" parameters (N, K, dims)
- add "good" kmeans test data (without singularities: K > unique points)

* remove raw SSE2/NEON implementation from convert.cpp
  * remove raw implementation from Cvt_SIMD
  * remove raw implementation from cvtScale_SIMD
  * remove raw implementation from cvtScaleAbs_SIMD
  * remove duplicated implementation cvt_<float, short>
  * remove duplicated implementation cvtScale_<short, short, float>
  * add "from double" version of Cvt_SIMD
  * modify the condition of test ConvertScaleAbs

* Update convert.cpp

fixed crash in cvtScaleAbs(8s=>8u)

* fixed compile error on Win32

* fixed several test failures because of accuracy loss in cvtScale(int=>int)

* fixed NEON implementation of v_cvt_f64(int=>double) intrinsic

* another attempt to fix test failures

* keep trying to fix the test failures and just introduced compile warnings

* fixed one remaining test (subtractScalar)

* add accuracy test and performance check for matmul
  * add performance tests for transform and dotProduct
  * add test Core_TransformLargeTest for 8u version of transform

* remove raw SSE2/NEON implementation from matmul.cpp
  * use universal intrinsic instead of raw intrinsic
  * remove unused templated function
  * add v_matmuladd which multiply 3x3 matrix and add 3x1 vector
  * add v_rotate_left/right in universal intrinsic
  * suppress intrinsic on some function and platform
  * add pure SW implementation of new universal intrinsics
  * add test for new universal intrinsics

* core: prevent memory access after the end of buffer

* fix perf tests

cv::rand result is not bitexact for floating-point numbers

cv::rand result is not bitexact for floating-point numbers

a JSON emitter, a parser, tests and some basic doc.

Modified performance test and solve a problem caused by an enum type.

For faster test

Major changes:

- modify the Base64 functions to compatible with `cvWriteRawData` and so
on.
- add a Base64 flag for FileStorage and outputs raw data in Base64
automatically.
- complete all  testing and documentation.

  * loosen the threshold only under aarch64
  * fix #6610

Fix for bug #5007: moved definition of Size_MatDepth_t and Size_MatDepth from ts_perf.hpp to perf_channels.cpp. This way they are closer to where they are needed and live in a different namespace (possibly the reason why the fix works).