Flaskbotrc is a file containing config of all active
outgoing webhook bots. It is used to provide configuration
of all active outgoing webhook bots to zulip-bot-server.
Add 'Type of bot' option for bots by adding dropdown option in
settings->"Your bots". For now, this allows creating incoming webhook
bots in addition to default bots.
This will enable users to add a bot as an incoming webhook
(in addition to add full-featured bots).
With various minor tweaks and cleanups by tabbott.
Fixes#2186.