Grafting lets us work with older Tesseract versions as if they could use
sandwich, so there is no point in keeping it. It's been deprecated for a
long time now anyway.
Tesseract 3.05.01 backported the textonly_pdf=1 which allows the use
of this superior PDF renderer prior to 4.00 alpha. This means that
the tess4 name is no longer accurate, so call it a sandwich because of
its merge-preserve characteristic. Preserve the tess4 name. Fix the
documentation and tests to reflect this.
Make it the default, because it’s better. It does not have the issues
the “tesseract” renderer does prior to Tess 3.05.00 with rendering
PDFs that Ghostscript corrupts, and it produces better output without
re-rastering.
Deprecate some old stuff to avoid the test suite growing obscenely
large.
