[#409] Resolve "Eliminate diceware channel names"

context

• after getting rid of channel names and descriptions we ran an experiment to provide channels with diceware names in order to provide a memorable but random identifier for a channel
• however, we received feedback that the diceware names were confusing + distracting to subscribers of these channels, so we opted to get rid of them!

changes

• migration to remove channel names
• looked for instances in the code that refer to channel names (mostly notifications) and removed those
• looked thru splash and privacy policy to remove references to names

closes #409 (closed)