Make RF model gpu-friendly.

[charleskawczynski]

#1212 made the RF model use ordinary arrays, which cannot reside on the gpu, and allows the EDMF model to be non-isbits. We should think about how to use static data structures without paying such a steep compilation cost. #1211 was an attempt, however, it seems like we may need to write custom data structures and define an equivalent LinearAlgebra.dot for it.