Adds a note about auto-notification messages that are sent when
these general settings are changed for a stream: name, description,
access and posting permissions, and message retention.
Uses new `select-stream-view-general.md` for instructions.
Also, updates description to include web-public streams with link
to documentation about them, and clarifies location of button/icon
as well as the header for the privacy setting in the update modal.
Finally, updates save instruction to use `save-changes.md` and
renumbers instructions list to only use '1'.