fix #36746, link to handbook 2.0
remove unused stack-down action. Added here but never implemented http://sourceforge.net/p/mscore/code/4066/
fix #36656: width (of lines) vs. thickness

and consolidate volta "Continue height".
Also change "Fix" to "Fixed" to make clearer it is an adjective, not a
noun or verb.
And make "Numbers only" Sentence style.
Get rid of unneeded abbreviations "Visib." and Link."