[com1]: make entrainable deposition for snow avalanches reasonable

[PaulaSp3]

In PR #1292 the option for entrainable/erodable deposition is added (if ent in simTypeList, adaptSfcStopped = 1, adaptSfcEntrainment = 1, entrainableDeposition = True).

Then automatically the topograpy is adapted to erosion and deposition (when erosion takes place, the topography (DEM) results from the difference of the original topography and the corresponding erosion depth).

When computing with snow avalanches, it makes more sense to add an "snow layer on top of the topography from that a part is entrainable) because snow avalanches do not modify the the topography.

[fso42]

Just a note: for avalanches (at the moment) it's not really a layer as such: the DEM, i.e. the surface the particles "experience" is never changed. There is no difference DEM-wise whether a particle flows over an entrainment area vs a non-entrainment area...