The user option `spatialEpisim.foundation.datapath` for storing Persistent User Data is not canonical

[bryce-carson]

Deprecate the option "spatialEpisim.foundation.datapath" and use the canonical locations for data which is persistent across sessions (see the appropriate section in the r-pkgs books).

[bryce-carson]

I was inspired to use such an option by the geodata package, but that package is apparently not following best practices (using a canonical path).

During testing I felt how a user of our package might feel if we follow geodata's example; it's not a great idea to use a customization option like this for persistent storage paths. I experienced a number of annoying errors and needed to look at documentation; the package should've just used a standard storage location on my computer, like other GNU packages do.