Serialize after running other exports, as patch path is embedded in dataframe; write this with subdirectory

This reverts merge request !16

Exporting patch masks does not automatically make a PatchStack, which forces them to all be the same size

By default, return non-expanded patches and masks; allow contour and mask overlays in non-expanded patches

Standardize patch (mask) getters return ad-hoc DataFrames, and _acc methods wrap these in PatchStack accessors (which automatically become shape of largest patch)