[sponge] Improve spong  - Make sponges able to suck river water  - Fix #281
[sponge] Improve spong
 - Make sponges able to suck river water
 - Fix #281

Coethium/server-minetestforfun,LeMagnesium/minetest-minetestforfun-server,sys4-fr/server-minetestforfun,sys4-fr/server-minetestforfun,LeMagnesium/minetest-minetestforfun-server,Coethium/server-minetestforfun,crabman77/minetest-minetestforfun-server,MinetestForFun/minetest-minetestforfun-server,MinetestForFun/server-minetestforfun,Gael-de-Sailly/minetest-minetestforfun-server,crabman77/minetest-minetestforfun-server,sys4-fr/server-minetestforfun,Gael-de-Sailly/minetest-minetestforfun-server,MinetestForFun/minetest-minetestforfun-server,MinetestForFun/server-minetestforfun,Coethium/server-minetestforfun,Ombridride/minetest-minetestforfun-server,Ombridride/minetest-minetestforfun-server,LeMagnesium/minetest-minetestforfun-server,Ombridride/minetest-minetestforfun-server,crabman77/minetest-minetestforfun-server,Gael-de-Sailly/minetest-minetestforfun-server,MinetestForFun/minetest-minetestforfun-server,MinetestForFun/server-minetestforfun