rename wrcc_leaflet() to raws_leaflet() and make it generic

[jonathancallahan]

We would like to be able to use the leaflet map with metadata from either fw13 or wrcc sources.

Please rename wrcc_leaflet() to raws_leaflet() and make it smarter so that it will do the right thing with either type of metadata dataframe. I imagine there will just be a big if-else in the function to set up the following:

• chose the proper column to use as the unique identifier (nwsID or stationID)
• create the popup dialog to use these names

Are there other improvements that could be made in this function? I'm open to suggestions.