Recolored 18w43a Sand & Sandstone

In this snapshot, only sand and sandstone types received new textures, while red sandstone variants at the time were still using textures from an earlier texture update test release. For consistency, alternative red sand and sandstone textures have been included in the _textures_ folder to fix this.

To add them in, drop the selected textures into the _block_ folder to replace the current textures.

Sandstone is the only block that uses connected textures by default. To make the alternative red sandstone texture connect, move the _red_sandstone_ folder from the _optifine_ folder into the _ctm_ folder.