Corrected, updated and uniformized documentation.

bob/learn/em/empca_trainer.cpp

bob/learn/em/gmm_machine.cpp

bob/learn/em/gmm_stats.cpp

bob/learn/em/isv_trainer.cpp

bob/learn/em/ivector_machine.cpp

bob/learn/em/jfa_trainer.cpp

bob/learn/em/kmeans_machine.cpp

bob/learn/em/linear_scoring.cpp

bob/learn/em/map_gmm_trainer.cpp

bob/learn/em/plda_base.cpp

bob/learn/em/plda_machine.cpp

bob/learn/em/train.py