Update scientific methods in Connectivity datatype

Currently this functionality is not visible through the web interface.
However, in connectivity scientific there is a method to normalize the
weights/distances in the corresponding connectivity matrix.

Normalization by in-degree. This is in fact the normalisation mode called
'region'. It's done more often than not, and very little spoken of ... This
normalizes the cumulative input (sum) to 1, that is the coupling term is a
weighted average. It helps to constrain the range of the global coupling
strength to [0, 1].