Fixed equations, deleted some temporary variables to reduce memory usage, used eval() function to improve readability.

run_samir() operational. Outputs are not yet valid, updated dev_samir_xarray.ipynb for comparison with modspa excel and added validation inputs and outputs for comparison.

Modified input calculations. Reprojection of weather dataset needs to be handled differently for bigger images (with OTB for example). Modified the parameter class. Begining to work on samir time loop, inputs and parameters are done. Added env file. New method for calculating ET0 with xarray might have been found.