Add support for separate/custom calibrations per Landsat image

[cgmorton]

There is currently no way in the workflow to set non-default hot/cold Kc values for calibration. This was originally done since the Monte Carlo script was adjusting the Kc values internally for each image.

[cgmorton]

The original approach for running pymetric was to have a separate "metric" INI file for each Landsat image, and the Kc values were set in the INI file (so you could have unique Kc values for each image). We then simplified this approach for running the Monte Carlo scripts on the NEX and generated a single INI file for all images in the year/path/row, but this removed the ability to manually adjust the Kc values.

We could modify the workflow to go back to using separate INIs for each image. This would probably be fairly simple to implement, but generally the Kc values are the only thing you would change between images and this would create a lot of extra files of the same exact values/parameters.

We could add a "Kc" field to the hot and cold pixel shapefiles. The benefit of this approach is that it keeps the hot/cold pixel locations and Kc values in one place. This would also be fairly simple to implement. One small problem with this is that you have to open ArcGIS or QGIS in order to adjust the Kc values, but this may not be that big of a deal since you will also have to use the programs to move the points.

Finally, we could define a new file (txt, json, csv, etc) in the main image folder or in the PIXELS folder that contains the Kc values.