more appropriate fuel levels

[theTrav]

Currently ovens, smelters, tanning tubs and probably many other things can hold many times more fuel than is needed for any current use.
Yes most people exploit the bugs that let you use them with only one tick of fuel, but for new players it seems that over fueling is the default action.

Please reduce the limit to something more reasonable and then increase it again when you add things that take longer to cook/melt/process