Add options for txt, pdf, and hocr output

[ElectricRCAircraftGuy]

Sample run to output all 3:

tesseract Selection_1.png out txt pdf hocr

produces:

out.hocr
out.pdf
out.txt

Make my options to pdf2searchablepdf like this:

• --txt - also output .txt
• --pdf [default] - actually, don't have this option, just have --pdf ALWAYS ON instead, and add a --no-pdf option to turn it off!
• --hocr - also output .hocr

So:

1. txt ONLY would be --txt --no-pdf
2. txt and pdf would be --txt
3. hocr ONLY would be --hocr --no-pdf
4. hocr AND txt but NOT pdf would be --hocr --txt --no-pdf
5. all 3: hocr, txt, and pdf, would be --hocr --txt