Improving image generator

[danschultzer]

This adds the missing features discussed in #30.

The rotation and gradient already cause problems for OpenCV preprocessor so it might be a good idea to try to improve the preprocessor already.

[codecov-io]

Codecov Report

Merging #45 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #45      +/-   ##
=========================================
- Coverage    98.7%   98.7%   -0.01%     
=========================================
  Files          16      16              
  Lines         463     462       -1     
=========================================
- Hits          457     456       -1     
  Misses          6       6

Impacted Files	Coverage Δ
lib/image_processor/preprocessor/opencv.js	99.36% <100%> (-0.01%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update be22b50...b4ec43c. Read the comment docs.

[danschultzer]

Also, this can be run now to speed up benchmark: npm run benchmark -- --preprocessors opencv --verbose

Useful for testing.

With the current seed of 474523310 I get 70% success rate:

npm run generate-benchmark-sample -- --seed=474523310
npm run benchmark -- --preprocessors opencv --verbose

[danschultzer]

Added ability to disable modifiers to ease up testing a variety, and check success rate for certain traits.