Add moving_window function

[ninbrm]

Function to run connected_landscape or betweenness_ as a moving window over a landscape.
It relies on two helper functions:

1. make_landscape: which creates an Array with a quality, affinity, and optionally a cost layer for input to moving_window
2. clip_landscape: which clips a window from the landscape and returns it as a dictionary for the parallel version of the moving_window_helper
3. moving_window_helper: which is the actual workhorse, takes either a landscape clip (for parallel computation) or a window tupple.