Support for diversions in SFRmaker

This issue is opening a discussion that seeks to add support for diversions within SFRmaker. The attached shapefiles correspond to the grid and linework used in a hypothetical model first [published in 2016](https://doi.org/10.1016/j.envsoft.2016.04.018). There are several attributes within both shapefiles, this is left over from an attempt by the NVWSC to write a python script that would generate SFR input. That effort wilted years ago.

In the grid shapefile, there are three attributes that are pertinent to SFRmaker (I think). The first is "Elevation," which defines the altitude of land surface for every cell. The second is "Reservoir" which is a flag indicated which cells are lake cells. This may not be needed at the moment, but might help guide support for establishing SFR/LAK connections? The third attribute is "Active_cell" which is essentially Ibound.

Regarding the linework representing the river, tributaries, and canals, there is an attribute titled "StreamType" which can take on an integer value between 1 and 4:

1. River
2. Tributary
3. Diversion
4. Thalweg of lake

One other attribute of note is "StrTop_Off." This was an attempt at defining how much incision to apply to the segment (where "segment" fits with the old SFR2 paradigm. Having not used SFRmaker in the past, I suspect these two shapefiles may need to be supplemented with additional data to explore what it might take to get diversions into SFRmaker. I would be happy to work on that.

All of the other attributes present in the files likely can be ignored.

Here is what the grid & linework look like (flow is from left to right):


I'm hopeful these example shapefiles could serve as a small test case for incorporating diversions into SFRmaker, particularly for generating MODFLOW 6-compatible input? While this example is small, many (most?) western US basins have diversions of some form, and so I think this would be a popular addition.

[example_grid.zip](https://github.com/usgs/sfrmaker/files/6192585/example_grid.zip)
[example_linework.zip](https://github.com/usgs/sfrmaker/files/6192586/example_linework.zip)