Update git-annotate/git-blame documentation

Update git-annotate/git-blame documentation

Moved options that pertained to both git-blame and git-annotate to a
common file blame-options.txt.

builtin-blame.c: Removed --compatibility, --long, --time from the
short usage as they are not handled in the code.

Documentation/git-blame.txt: Removed common options to git-annotate.
Added documentation for --score-debug.  Removed --compatibility.
Adjusted usage at top to not wrap on 80 columns.

Documentation/git-annotate.txt: Using common options blame-options.txt.

Documentation/blame-options.txt: Added -b note about associated config
option, added --root note about associated config option, added
documentation for --show-stats.  Removed --long, --time, --rev-file as
those options do not really exist.  Added documentation for -M/-C taking
an optional score argument for detection of moved lines.

Signed-off-by: Andrew Ruder <andy@aeruder.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>