Implement a way to downscale a selection of variables

[ArcticSnow]

The idea is to implement as part of topo_scale.py and dynamic way to select which variable to downscale and adapt accordingly the variable needed to download (speed up downloading).

This could be done by breaking the downscaling code in section of variables that are called upon need.

varout = ['t', 'sw', 'lw']

# add logic to check dependencies between variables

for var in varout:
      if var == 't':
           downscale_temperature()
     elif var == 'sw':
           downscale_sw()

This is an idea, and it is still unclear how to efficiently implement this. It may require to package the downscaling into a class and add inheritence.