speed increased and mb_profile + winter MB calib

[lilianschuster]

• increased the speed of TIModel_Sfc_Type by removing some pandas logics
• included MB profile calibration possibilities (not yet documented)
• included winter MB calibration (not yet documented): this works only locally at the moment!
• • added some more documentation

[lilianschuster]

• rewritten example workflow of TIModel_Sfc_Type -> see: https://github.com/OGGM/massbalance-sandbox/blob/master/docs/surface_type_distinction/oggm_sfc_type_bucket.ipynb