Improvements in scripts and bugfix for Furnaces

I've recoded some parts of the scripts. Now you can call them from other folders (like ./SportBukkit/compile.sh), and they will work even if the path contains whitespaces. When it has finished compiling, it will go back to the original folder you executed the script from. I've also created a "init.sh" that automatically removes the "build" folder and download the "base" folder if it does not exist.

The bugfix for Furnaces fixes BUKKIT-4243: if you get a Furnace BlockState and use setBurnTime to set the burn time from a zero to a nonzero value, the block won't be updated, and it will look like an idle furnace, even though it's actually burning. Right now I'm having to use dirty tricks which are far from ideal: https://github.com/socram8888/SolarFurnace/blob/master/src/main/java/ti/s4x8/bukkit/solarfurnace/FurnaceUpdater.java. I issued a pull request to Bukkit long time ago but looks like they're not interested in fixing this bug.