Merge branch 'bk/sob-dco'

Document that the meaning of a Signed-off-by trailer can vary from project to project in the end-user documentation, and clarify what it means to this project. * bk/sob-dco: Documentation: stylistically normalize references to Signed-off-by: SubmittingPatches: clarify DCO is our --signoff rule Documentation: clarify and expand description of --signoff doc: preparatory clean-up of description on the sign-off option