Docs: use consistent terms for rapid that are easier to understand.
add links to rapid move and feed rate when they are in a description.
fix a couple of typo's discovered along the way.

Signed-off-by: John Thornton <jthornton@gnipsel.com>
Docs: shorten link

Signed-off-by: John Thornton <jthornton@gnipsel.com>
docs: fix some typos in gladevcp docs