Cleanup SimpleBlocks/Items

- Added missing overridden methods
- Rearranged entries for getAddon/getIdentifier/getLocalizedName/getUnlocalizedName/getItemStackDisplayName/equals/hashCode to all be the last methods in their respective classes.
- Suppress compiler warnings
- Resolved lighting issues with slabs
- Resolved incorrect item drops for slabs
- Merged SimpleItemSlab into SimpleSlab
- Formatting changes

Signed-off-by: Steven Downer <grinch@outlook.com>
Update gradle-wrapper.properties to use Gradle 2.0

Signed-off-by: Steven Downer <grinch@outlook.com>
Add getter/setter for isPoweredOnly in SimpleDoor

This allows you to set the power requirement of the door outside of the constructor.

Removed the check against super.onBlockActivated, as it will always return true.

Signed-off-by: Steven Downer <grinch@outlook.com>