Fix only can pop only one fluids of each kinds of fluids.
Fix stacksize of FluidElement.getOutputStack()'s return value is 0.
Replace Vector3 with CoordTuple.
Merge pull request #261 from yushijinhun/fix-bugs

 Fix it only can pop one fluids of each kinds of fluids.
rework of the decay mechanic
Merge pull request #262 from way2muchnoise/1.7-update

rework of the decay mechanic