refs #830, #872, #876, #1125:
 * removed quantity and changed final unit to unit from sources (RealInput) and sensors (RealOutput) again (where there was no quantity and final unit in MSL 3.2) (Unfortunately not consistent throughout the MSL 3.2 at all)
 * introduced sensible units for sources (RealInput) and sensors (RealOutput) where applicable
 * fixed comment errors in MultiBody.Joints.Internal.PrismaticWithLengthConstraint

git-svn-id: https://svn.modelica.org/projects/Modelica/trunk@6802 7ce873d0-865f-4ce7-a662-4bb36ea78beb