Added extra details around setting up admin user (#1937)
Added extra details around setting up admin user (#1937)

after running create-admin the user will be prompted to provide extra details and set the admin password
SingTel-DataCo/incubator-superset,mistercrunch/panoramix,alanmcruickshank/superset-dev,asdf2014/superset,BRD-CD/superset,zhouyao1994/incubator-superset,mistercrunch/panoramix,massgov/incubator-superset,nekia/incubator-superset-dev,dmigo/incubator-superset,apache/incubator-superset,asdf2014/superset,alanmcruickshank/superset-dev,ArijanaBrlek/superset,zhouyao1994/incubator-superset,timifasubaa/incubator-superset,apache/incubator-superset,apache/incubator-superset,airbnb/caravel,robert-digit/superset,robert-digit/superset,ArijanaBrlek/superset,SingTel-DataCo/incubator-superset,alanmcruickshank/superset-dev,zhouyao1994/incubator-superset,SingTel-DataCo/incubator-superset,nekia/incubator-superset-dev,BRD-CD/superset,mistercrunch/panoramix,airbnb/superset,ArijanaBrlek/superset,FrederichCheng/incubator-superset,timifasubaa/incubator-superset,timifasubaa/incubator-superset,zhouyao1994/incubator-superset,FrederichCheng/incubator-superset,robert-digit/superset,airbnb/caravel,SingTel-DataCo/incubator-superset,nekia/incubator-superset-dev,asdf2014/superset,alanmcruickshank/superset-dev,BRD-CD/superset,airbnb/superset,airbnb/superset,airbnb/superset,airbnb/caravel,ArijanaBrlek/superset,apache/incubator-superset,mistercrunch/panoramix,massgov/incubator-superset,BRD-CD/superset,asdf2014/superset,zhouyao1994/incubator-superset,dmigo/incubator-superset,apache/incubator-superset,timifasubaa/incubator-superset,nekia/incubator-superset-dev,massgov/incubator-superset,massgov/incubator-superset,FrederichCheng/incubator-superset,dmigo/incubator-superset,dmigo/incubator-superset,robert-digit/superset,airbnb/caravel,FrederichCheng/incubator-superset