In sim mode with wind, allow only AutoWind=Manual

This is a fix to a minor sim mode issue.  The problem is that if one circles in sim mode with AutoWind=Circling, after a couple of circles, the wind is reset to zero.  This fix makes it so that if the user creates wind in sim mode, AutoWind=Manual (by allowing only this option in the wind settings dialog).  While I was at it, I found and eliminated a duplicate help message for AutoWind.  I updated the help message to reflect this change and rewrote it a little.