Add tests for OCR

[marcincichocki]

There are no tests for OCR which is vital part of this project. We should ensure that most common resolutions are supported:

• 1080p
• 1440p
• 4k

That will propably require adjusting ./src/config.json for each resolution. In worst case it would require retraning tesseract.

Day 1 notes:

• 1080p, 1440p and 4k mostly work on existing code, small improvments necessary
• grid and daemons OCR works very well, no issues there(some edge cases on 4k since res is so high, tesseract recognize some leftover junk, but it's mostly fixed by separate threshold for each res)
• buffer OCR is a mess, It will require separate .traineddata because it's so bad(it's a miracle that it worked so well anyway)
  

Day 2 notes:

• buffer ocr scrapped, reimplemented by counting raw pixel data(size of buffer scales with resolution). Ocr might be used later on as fallback
• much more reliable than ocr, but requires very specific threshold
• still need to check impact of gamma correction on this method