update player list in lobby gracefully for better user experience
fixed child removal
fixed relayout on draw
refactored child remove/replace into ScrollPanelWidget
fixed scrolling on child remove
added moving average to contrails to smooth them when aircraft are circling
put attack traits into the syncreport.log
refactored Average method in PPos
Merge pull request #2798 from bidifx/contrail

smooth contrails
Merge pull request #2796 from Mailaender/attack-sync

Put attack traits into the syncreport.log
Merge pull request #2789 from bidifx/lobby

update player list in lobby gracefully for better user experience