Add evaporationRate control pipe command

This replicates the -evr command line argument as a control pipe command
so that the evaporation rate can be changed in a running sandbox.

Because negative evaporation values are accepted, another way to use this
control pipe command is for global rain.

Signed-off-by: Sean Robinson <sean.robinson@scottsdalecc.edu>

Sandbox.cpp

@@ -1320,6 +1320,15 @@ void Sandbox::frame(void) {
                         std::cerr << "Wrong number of arguments for dippingBedThickness control pipe command" <<
                                   std::endl;
                     }
+                } else if (isToken(tokens[0], "evaporationRate")) {
+                    if (tokens.size() == 2) {
+                        double evaporationRate = atof(tokens[1].c_str());
+                        if (waterTable != 0) {
+                            waterTable->setWaterDeposit(evaporationRate);
+                        }
+                    } else {
+                        std::cerr << "Wrong number of arguments for evaporationRate control pipe command" << std::endl;
+                    }
                 } else {
                     std::cerr << "Unrecognized control pipe command " << tokens[0] << std::endl;
                 }