Disable buttons when none selected, remove horizontal scrollbars

[cheshire137]

• Disable 'Tasks' and 'Filters' top nav buttons when the user has not provided an access token.
• Make top navigation area more compact vertically.
• Get rid of horizontal scrollbar around filter select menu.
• Disable 'Snooze', 'Archive', and 'Ignore' buttons when no visible tasks are selected.
• Disable 'Restore' button when no hidden tasks are selected.
• Use an emoji for the refresh button icon.
• Spell out 'View hidden' instead of using an eye Octicon.
• Move 'View hidden' button below filter select menu.
• Get rid of rounded corners in top navigation, as well as borders adjacent to the window edges on the top nav buttons.
• Display page titles for edit filter, new filter, and 'manage filters' views.
• Make 'Authenticate' view less noisy by removing green styling on 'you are signed in' message.

/cc @probablycorey @summasmiff

[summasmiff]

Looks like we lost the "Hidden Tasks" eye icon. I had moved it to be next to the Refresh icon on the secondary toolbar.

I see now that it is a text link. I can't read good today.