Plan functionality to link points lines and polygons to the network.

[dblodgett-usgs]

There is a suite of network linking functionality that would be helpful as a general set of utilities.

I've implemented a pretty good method for points over here: https://github.com/dblodgett-usgs/nwm_subset/blob/master/nexus_locations/collate_sites.R

Could probably pull in some functionality directly from or inspired by: https://github.com/lawinslow/hydrolinks

Could look into using the event web services employed by the HydroLink tool -- use this notebook for inspiration: https://github.com/dwief-usgs/batch-hydrolink/blob/master/nhd_batch_hydrolink.ipynb

The EPA has developed some nice methodologies for catchment-based indexing -- see figure 14 here: https://www.epa.gov/sites/production/files/2016-04/documents/final_geopilot_report_2016-03-21.pdf

This issue can be closed when the basic function input/output and algorithm has been laid out in a new set of issues. Basic planning should take place in the comments of this issue and possible taken out to a wiki page or some roughed in roxygen.

[dblodgett-usgs]

This is done enough. #19 and DOI-USGS/hydroloom#16