Blob Tweaks

 * Blobs can expand into space again but it will be harder to do than on a space tile. EngiBorgs could RCD the floors under the blob to stop it from expanding, which is fatal if it manages to get near the core and open a way to it.
 * Dead robots will be gibbed in their blob_act() as their bodies will block the blob.
 * Reduced the damage the blob takes from explosions, and increased the brute resistance. Blobs main weakness is fire, not force.