stbt.ocr: Support command-line flag change in tesseract 3.05
stbt.ocr: Support command-line flag change in tesseract 3.05

> Changed tesseract command line parameter '-psm' to '--psm'.

https://github.com/tesseract-ocr/tesseract/wiki/ReleaseNotes#tesseract-release-notes-feb-16-2017---v30500

N.B. Ubuntu 16.04 has 3.04.01; 18.04 has 4.0.0-beta.

stb-tester/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester,stb-tester/stb-tester