git-gui: Improve our labeling of blame annotation types

git-gui: Improve our labeling of blame annotation types

It feels wrong to call the -M -C -C annotations "move/copy tracking"
as they are actually the original locations.  So I'm relabeling
the status bar to show "copy/move tracking annotations" for the
current file (no -M -C -C) as that set of annotations tells us who
put the hunk here (who moved/copied it).  I'm now calling the -M
-C -C pass "original location annotations" as that's what we're
really digging for.

I also tried to clarify some of the text in the hover tooltip.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>