index.htm: clean up trailing whitespace
index.htm: edit `More Details` section

Fixed grammar, phrasing, and source text formatting (for readability and
easy editing).
download.htm: clean up trailing whitespace
getstarted.htm: clean up whitespace
principles.html: clean up whitespace
zebra.htm: clean up whitespace
getstarted.htm: cleanup, rephrase, reformat
principles.htm: cleanup, rephrase, reformat
zebra.htm: cleanup, rephrase, reformat