Added rawLinAlgAddMult, rawLinAlgSubMult.

Code for ffpack is Jakob Kroeker's.  Also, mult of MutableMatrices gives
an error, instead of an uncaught exception now.  Code is not yet tested.
removed addMultipleTo ; it does not matter anyway, because this file is not used
added addMultipleTo interface
added some printots and two assertions. printouts should be replaced by a logger, which is configurable from M2)
removed old addMultipleTo interface
removed old addMultipleTo interface
removed old interface and added a printout (to be replaced by a configurable logger)
added call to  LinAlg::addMultipleTo
added 'mult' and renamed old (nonfuncitonal) interface addMultipleTo to  addMultipleToExt
merged with linalg from Mike