Implement optional corrections (SET, iono, tropo) methods (#80)

* Add extracting optional correction layers and prep_aria.py method for loading to MintPY

* Applying optional corrections and before-after correction plots
Change the CDSAPI URL to the latest to enable ERA5 corrections via PyAPS

* Fix colorbar label in comparison plots

* change mintpy template to dictionary. add checks if files exist and separate inputs

* add reference date selection, plot corrections, move applying corrections outside the calculations, plot estimated velocities for visual inspection.

* change my_sites.txt and me.txt file locations

* change my_sites.txt and me.txt file locations

Author: ehavazli