Uses the recommended rules apart from complexity/useArrowFunction,
which would affect about 1700 lines of code with little benefit
right now. This is something that can be addressed over time.
The previously-scattered image opening logic has been refactored to a
single ImageDescriptor struct/Object available to both JS and C++ code
This removed about 150 LOC but more importantly reduces the complexity
of adding/exposing new operations that require an input image.
