cosmetics: add docu for shash::ContextPtr copy-ctor
cosmetics: add docu for shash::ContextPtr copy-ctor

trshaffer/cvmfs,DrDaveD/cvmfs,DrDaveD/cvmfs,cvmfs-testing/cvmfs,cvmfs/cvmfs,alhowaidi/cvmfsNDN,Moliholy/cvmfs,cvmfs/cvmfs,DrDaveD/cvmfs,Moliholy/cvmfs,MicBrain/cvmfs,cvmfs-testing/cvmfs,Moliholy/cvmfs,DrDaveD/cvmfs,cvmfs/cvmfs,cvmfs/cvmfs,reneme/cvmfs,MicBrain/cvmfs,trshaffer/cvmfs,cvmfs/cvmfs,djw8605/cvmfs,reneme/cvmfs,djw8605/cvmfs,Gangbiao/cvmfs,cvmfs-testing/cvmfs,djw8605/cvmfs,Gangbiao/cvmfs,djw8605/cvmfs,reneme/cvmfs,Moliholy/cvmfs,Gangbiao/cvmfs,DrDaveD/cvmfs,reneme/cvmfs,djw8605/cvmfs,trshaffer/cvmfs,cvmfs/cvmfs,trshaffer/cvmfs,Moliholy/cvmfs,cvmfs/cvmfs,MicBrain/cvmfs,DrDaveD/cvmfs,Gangbiao/cvmfs,cvmfs-testing/cvmfs,MicBrain/cvmfs,reneme/cvmfs,DrDaveD/cvmfs,alhowaidi/cvmfsNDN,Gangbiao/cvmfs,alhowaidi/cvmfsNDN,MicBrain/cvmfs,cvmfs-testing/cvmfs,alhowaidi/cvmfsNDN,alhowaidi/cvmfsNDN,trshaffer/cvmfs