Added .item:serializer module to automatically load and save item o…

…bjects.

Added parsers:
- [EnchantmentParser](item/serializer/src/main/java/it/angrybear/serializers/EnchantmentParser.java);
- [ItemParser](item/serializer/src/main/java/it/angrybear/serializers/ItemParser.java);
- [ShapeParser](item/serializer/src/main/java/it/angrybear/serializers/ShapeParser.java);
- [ShapedRecipeParser](item/serializer/src/main/java/it/angrybear/serializers/ShapedRecipeParser.java);
- [ShapelessRecipeParser](item/serializer/src/main/java/it/angrybear/serializers/ShapelessRecipeParser.java);
- [FurnaceRecipeParser](item/serializer/src/main/java/it/angrybear/serializers/FurnaceRecipeParser.java).
Added [YAGLParser](item/serializer/src/main/java/it/angrybear/serializers/YAGLParser.java) to automatically load parsers.
Fixed `Item#copy` with automatic resolution of interfaces: passing `Item` or `BukkitItem` will convert them into `ItemImpl` and `BukkitItemImpl`.
Fixed various bugs in **ShapedRecipe**.