[Sprint/InterestingIguana](chore): channel button UI adjustments

closes #1507 (closed)

• Prepares the channel sidebar to accommodate 'refer friends' button (to be added later)
• Moved settings cog up to the right of the username (where the edit pencil is on your own channel)
• Prevents 'complete your profile' button span from overflowing outside its border
• Stop showing the tag icon when the user hasn't selected any hashtags
• Deleted some styles that had been commented out for multiple years