Vanilla Connected Glass

Changed the item model to use default block models instead of the special glass one. This will not affect the block when placed, but is better for the item models because:

1. When multiple glass block items are down, this update will massively increase performance when compared to the original version
2. Multiple z-fighting in the item model will be fixed (there is still no z-fighting in the block model)
3. Any other visual issues will be fixed