Changes default outFilename to NDCesaro.h5 in calNDCesaro.py

and small modification
Implements more fitNDCesaro.py

Now fitNDCesaro.py can fit and output the ND results.
Plotting function is not implemented.
Probably will do it in another file, as well as the unit conversion.

Currently the units are in the GROMACS' units (ps and nm)