Improve select area visuals

[xenct]

Improve the aesthetics of plotting select_area. Eg remove boundaries of neighbouring regions (if desired)

Below, is an example of the current output. It is preferable to only plot the borders of the region you are interested in, or have the choice whether or not these other borders are shown.

A possible solution may be to select only the select_area in the regions object within the function (and drop the other areas).