SEMIC update 1.2

This update of SEMIC corrects for an error in the selection of the albedo schemes introduced with the previous version v1.1. Also it changed the Fortran primitive exp to its double precision version dexp in some instances.

Changes include

• if/else constructs where erroneous when introducing alb_scheme = "none", in the previous version (that flag is never checked); is now if/else if
• The refreezing parametrisation accounts the snowpack height (check if refreezing amount is smaller than snowpack height)
• change function call to exponential exp to its double precision version dexp
• refreezing fraction is always calculated, in case of no snow and additional epsilon term (variable epsil is the smallest double possible) prevents exceptions