Tag Alias: panting -> heavy_breathing

Aliasing panting to heavy_breathing. Both tags are in use, but heavy_breathing has more and has a wiki entry.

If anything, alias them both to breath, since you can't actually see heavy breathing or panting in a static image, but you can see the breath steam.

Looking over the tags, if we had the cold tag used more often, then we'd likely get fairly accurate results when with a breath -cold search when looking for images of panting.

I'd say keep them separate, as breath doesn't cover instances where the picture features "Haa~ Haa~" text.

Still waiting for a decision on this.

Aliased panting -> heavy_breathing for now, just to get them under the same tag, regardless of whether we change to breath.