add WeightMatrix and test
add WeightMatrixFromBinConverter as example
modify MaxEntSGDLearner, MaxEntSGDTrainInMemoryRunner and MaxEntSGDTrainWithCacheRunner to use WeightMatrix
modify MultiClassClassifierTestRunner to user WeightMatrix
fix bug in WeightMatrix
add option not to use bias term to SVMLightFormatToBinConverter
modify some files to use external bias vector
add some functions for handling float array to WeightVector and WeightMatrix