and remove *.TXT from backend/tools/data, adding GB2312.TXT
README
manual: try to make scaling info more exact, and re-iterate no text
printed for raster with scale < 1;
move CLI HRT section up;
add one-page docs/manual.html to git - should do same for 3.1M
manual.pdf??
other: remove some no longer used backend/tools, readme-cmake