Added UI for entering Slack webhook URL.
Added UI for entering Slack webhook URL.

ftiff/autopkgr,eahrold/autopkgr,lindegroup/autopkgr,HyppHere/autopkgr,lindegroup/autopkgr,HyppHere/autopkgr,ftiff/autopkgr,ftiff/autopkgr,lindegroup/autopkgr,eahrold/autopkgr,HyppHere/autopkgr,lindegroup/autopkgr,lindegroup/autopkgr,eahrold/autopkgr