- Moved from reach/ui to material/ui menu components, because reach ui wouldn't work with 2 menus
- This channel selector stores the default on settings
- setActiveChannelIfNotSet was deprecated, if the account has channels, it will always return a channel even if there is no active channel or stored channel
## Issue
535
## Change
- Header: Use the "channel list undefined" instead of "active channel url undefined" to determine if the button should be "pending".
- App: restore the use of `activeChannelClaim` instead of `activeChannelId`. In the existing design, the latter is never cleared is some situations, so the former is more accurate as it takes the current channel list into account. We might want to hide (not export) `activeChannelId` to avoid this mis-use again.
## Issue
Closes 627 account header doesn't refresh on sign up / log in
## Changes
Looking back at "[Header] Changes, fixes and improvements (#493)", noticed that old code was looking at `has_verified_email` instead of just checking whether an email exists. So, restored original code.
This does have a side-effect of the Logout button not showing any email address underneath it immediately after sign up (with the flow cancelled). But I vaguely recall it was that way previously. A refresh cleans it up.
Perhaps another `user/me` when leaving the Sign Up page can make everything in sync, but this PR simpler to test.
