fix pelican.server __main__ code, add deprecation warning
fix pelican.server __main__ code, add deprecation warning

getpelican/pelican,ingwinlu/pelican,avaris/pelican,iKevinY/pelican,talha131/pelican,getpelican/pelican,farseerfc/pelican,talha131/pelican,farseerfc/pelican,ingwinlu/pelican,avaris/pelican,iKevinY/pelican