[GSoC] OpenCV.js: WASM SIMD optimization 2.0

* gsoc_2020_simd Add perf test for filter2d

* add perf test for kernel scharr and kernel gaussianBlur

* add perf test for blur, medianBlur, erode, dilate

* fix the errors for the opencv PR robot

fix the trailing whitespace.

* add perf tests for kernel remap, warpAffine, warpPersepective, pyrDown

* fix a bug in  modules/js/perf/perf_imgproc/perf_remap.js

* add function smoothBorder in helpfun.js and remove replicated function in perf test of warpAffine and warpPrespective

* fix the trailing white space issues

* add OpenCV.js loader

* Implement the Loader with help of WebAssembly Feature Detection, remove trailing whitespaces

* modify the explantion for loader in js_setup.markdown and fix bug in loader.js