Optimize formation regrouping

[Josef Kufner]

When formation is walking somewhere and is given another command somewhere else, all units start running around like crazy, becouse their positions in new formation are very different from their previous positions. This is well observable when walking in wide formation back and forth -- units do not turn backwards but they swap sides (which is understandable, but redundant).

There should be some optimization of rearranging the formation on a new command.

[historic_bruno]

Formations will be completely redesigned or scrapped in the future, so basically anything they do now should be ignored :)