[PATCH] Improve ship sinking.

[wraitii]

A small optional change to the decay component to make the ship sinking look a lot better: basically the ship will first roll a little and then sink bottom first. Looks way more natural (though not really excellent either, just takes the anim to "waaaaay too ugly for this game" to "allright").

The patch makes it work with an optional line in the template, could be made default for any floating thing instead.

[peter]

In 13478:

Improve ship sinking. Patch by wraitii. Fix #1921

[wraitii]

In 13584:

Fake randomization of the ship sinking animation to make it look better with ship formations. Refs #1921