Fix bug #29 (lake center elevation)
Assign moisture initial algorithm
specificities of a process test (preconditions, updated map) now reified as a trait
Generate rivers requires a distance to coast > 0 (or may lead to no river at all)
test for the moisture assignment process
redistribution does not match what is expected => forgot about it
assignMoisture now supports relevant propagation function for soil moisture
aquifers added to add underground moisture
Merge branch 'feature/assign-moisture' into develop