Minor improvements

[va-li]

Proposed changes:

• Allow using *.tiff (not only *.tif) images, Pillow supports them
• Image paths were sorted only before being used in the corner detection, breaking the connection between the order of processed images and the order they are written in to the result JSON. (Probably the sorting before iterating over the data variables in different parts of the code can be removed.)
• When no valid pattern was detected by the linear estimation, numpy would show a RuntimeWarning that the mean of an empty slice was calculated, which was a hint for the following problem:
• When no valid pattern was detected by the linear estimation, the code for get_taylor_linear() would crash, because it's valid: List[bool] argument was in fact None. This was fixed with a check if the linear estimation was successful, and in case it was not an error is logged prompting the user to check the input images and the program now raises a ValueError