Now removes old crosswalk engine plugin when doing an add. Upgrade command now removes old engine, and installs latest.
Now removes old crosswalk engine plugin when doing an add. Upgrade command now removes old engine, and installs latest.

lewisl9029/ionic-cli,kublaj/ionic-cli,nihgwu/ionic-cli,MrGang1992/ionic-cli,guaerguagua/ionic-cli,isathish/ionic-cli,luciky/ionic-cli,luciky/ionic-cli,ebulay/ionic-cli,livebs/ionic-cli,baby518/ionic-cli,FeiHuang2012/ionic-cli,jfcisternasm/ionic-cli,xdyzy/ionic-cli,kapilcr123/ionic-cli,TurtleFromBupt/ionic-cli,misaxi/ionic-cli,tswordyao/ionic-cli,kapilcr123/ionic-cli,bopo/ionic-cli,jorgecasar/ionic-cli,ebulay/ionic-cli,jetlee0797/ionic-cli,lackyhuang/ionic,kublaj/ionic-cli,FeiHuang2012/ionic-cli,fanhaich/ionic-cli,fanhaich/ionic-cli,nihgwu/ionic-cli,xiaojian001/ionic-cli,isathish/ionic-cli,guaerguagua/ionic-cli,daew823/ionic-cli,lackyhuang/ionic,gyh000/ionic-cli,zckrs/ionic-cli,dezynetechnologies/ionic-cli,tswordyao/ionic-cli,xdyzy/ionic-cli,jorgecasar/ionic-cli,yangchengwork/ionic-cli,kennyhui/ionic-cli,wrousseau/ionic-cli,lackyhuang/ionic1.6.6,livebs/ionic-cli,baby518/ionic-cli,rbose85/ionic-cli,daew823/ionic-cli,csantanapr/ionic-cli,lewisl9029/ionic-cli,jfcisternasm/ionic-cli,xiaojian001/ionic-cli,misaxi/ionic-cli,rbose85/ionic-cli,linxing58/ionic-cli,wrousseau/ionic-cli,TurtleFromBupt/ionic-cli,jetlee0797/ionic-cli,lackyhuang/ionic1.6.6,huangzz/ionic-cli,gyh000/ionic-cli,MrGang1992/ionic-cli,linxing58/ionic-cli,yangchengwork/ionic-cli,huangzz/ionic-cli,dezynetechnologies/ionic-cli,csantanapr/ionic-cli,kennyhui/ionic-cli,zckrs/ionic-cli,bopo/ionic-cli