Changing sequence of images in as_pasture0 files.
1. Since pastures will now start from a different image in the sequence
depending on its rotation, they will be out of sync with any pasture with
different rotation.
2. If multiple buildings are placed on the map using the shift key all of
them have the same rotation, hence such pastures will be synchronised.
3. I have just changed the sequence, generating new sheep movement for each
rotation might yeild better results.
Merge pull request #2279 from nruprao/master

Changing sequence of images in as_pasture0 files.  Partly fixes #2256.