Validate files being processed

[neokabuto]

We need a way to check files the user inputs. Testers found that it's not unlikely that someone will use the wrong image unintentionally, so we need to make sure it's right.

-Rainfall/vegetation/etc images are just grayscale, so color images are obviously erroneous

-File names from DF will have a naming pattern, which can be matched

-Dimensions of images should all match