"Branch Coloring" should gray out the text as well

In "Branch Coloring" mode, the log line of the branch is in bold black, while other branches are in soft gray.  To make it easier for the eye to scan through, the commit text of the other branches should be grayed as well.

However, grayed text is already taken up by merge-commits, so the change of behavior may be confusing for existing users.  But in my opinion, graying out a merge-commit doesn't mean much, and I would rather have the grayed behavior taken up by this RFE.