[GRASS-dev] SIMWE update in grass7

[Soeren Gebbert]

Hi,
i have reactivated a long disabled feature in the grass7 SIMWE
library. Now the generation of walker vector point output is available
again. I have updated the spearfish example located in the r.sim.water
directory, using paraview makes it very easy to visualize the time
step output of the spearfish example.

Please test the modification and report any issue.

Still missing is the support of observation points logging the water
depth and discharge and a general code cleanup and re-fracturing.

Best regards
Soeren