Enh: improve docu and add pictures
Enh: improve docu and add pictures

LorenzE/mne-cpp,mne-tools/mne-cpp,mne-tools/mne-cpp,chdinh/mne-cpp,LorenzE/mne-cpp,mne-tools/mne-cpp,mne-tools/mne-cpp,chdinh/mne-cpp,chdinh/mne-cpp,mne-tools/mne-cpp,LorenzE/mne-cpp,LorenzE/mne-cpp,chdinh/mne-cpp,chdinh/mne-cpp,chdinh/mne-cpp,mne-tools/mne-cpp