We had never-enabled code to allow users to set default
streams for their bots (for event registration, default sending, etc.).
This commit removes the code.
Change applies to both subdomains and non-subdomains case, though we use
just the EXTERNAL_HOST in the non-subdomains case if there is only 1 realm.
Fixes#3903.
Added new option to download .zuliprc file directly from settings
page. This should help reduce friction when setting up new
bots/integrations. This new feature is available in the bot cards and
the 'show your API key' section. One caveat is that the filename is
automatically set to 'zuliprc' instead of '.zuliprc', since as most
browsers do not allow filenames to start with a dot.
Fixes#2327.
The data-name attribute in this case allows for a particular settings
section element to show up when the appropriate sidebar category is
clicked (which will have the same value in the data-section key).