Implement item enchantment

[Smjert]

All the informations needed are here: http://www.minecraftwiki.net/wiki/Enchanting

The only strange thing is that according to all that formulas you can have a maximum modified level of 75, increased by the factor up to 93.75 (even if pre-release 5 code shows that he always adds 0.5 to the number), but you can have level V Efficiency where the maximum range is way higher than that value.
Should see the 1.0 code.