Add versatility to create_map

[troyhill]

• option for simple plotting of locations (without measurement or characteristic counts)

• provide a characteristic and plot data for that parameter

• option to return the coordinate data

• option for word-compatible output? Can also handle this in a document.

• add region 8 shapefile to package data & use for identifying odd coordinates

[troyhill]

@ethanwhyu I added create_map_alt that addresses the first two bullet points above. It has options for creating a basic plot just showing locations (parameter = NA), or if a parameter argument is provided it returns a plot showing median values for each site and some distributional information. Maybe a similar approach is useful for revising the (non-alt) create_map function. When that's resolved we can delete create_map_alt.