MRG : deprecations for v0.9

it's still WIP

It is unclear what should be now the behavior or stc_to_label given that there are still some tests for the old behavior on which depend new ones.

I also need to fix the example of connectivity that uses the old viz function
As far as I can see the test only covers very superficial properties of the resulting labels (number of labels), couldn't it just as well be run with the new setting (instead of including the old `_stc_to_label`)?