add finite water feature toggle and auto-detect code

autodetect-finite-water.lua

@@ -0,0 +1,9 @@
+-- enable finite liquid in the presence of dynamic liquid to preserve water volume.
+local enable = false
+
+if minetest.get_modpath("dynamic_liquid") then
+	pipeworks.logger("detected mod dynamic_liquid, enabling finite liquid flag")
+	enable = true
+end
+
+pipeworks.toggles.finite_water = enable