README: Include link to ISO standard for SI units
README: Include link to ISO standard for SI units

+ more consistent capitalization of texts

N.B. Fixed in spec but generated files were not re-generated (see
previous comment)

Signed-off-by: Gunnar Andersson <df6c1dc70ee3404c16d7de0a5a8d978b44fa18d4@genivi.org>

GENIVI/vehicle_signal_specification,GENIVI/vehicle_signal_specification