Minor fixes

[jcoulter12]

A handful of minor fixes, including:

• minor improvements to the tutorials
• deltaPath previously had units in the documentation, however should not have because it's in crystal coordinates
• Clearer instructions on how to use post-processing python scripts, plus minor updates to the scripts themselves
• Minor improvements to error messages
• A clear warning for phonopy runs where primitive and unit cells are not the same
• Remove primitive_matrix=auto option in ml transport tutorial, as it's sometimes problematic.
• Added isotope scattering citation to output