Prompted by Creators-of-Create/Create#1712

When vertical slabs are added to a Create contraption which is rotated and placed back down, their orientation is rotated 180 degrees from what it should be.
It seems that this line which was added to fix an earlier issue is causing this:
https://github.com/Vazkii/Quark/blob/bb564ebabed12c1c2090792e1f1e43796f9c7266/src/main/java/vazkii/quark/content/building/block/VerticalSlabBlock.java#L68

Additionally, the mirror method of VerticalSlabBlock seems to ignore the axis the block is being mirrored over, which is causing further incorrect orientation issues when the blocks are used with Create's Wand of Symmetry.