Fix bug with calibration-viewer.py, monthly plots, adjusting window size.
Fix bug with calibration-viewer.py, monthly plots, adjusting window size.

Previously, there was an error when trying to change the "expanding window"
plotter to a "fixed window" plotter for monthly plots. The problem had to
do with not type casting window_size_yrs to an Int, so the operation
was happening on a string instead and failing.

tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem,tobeycarman/dvm-dos-tem