Fix some small notification / token issues

Summary:
Fixes T3218.

• Currently, Paste pages don't clear notifications about the paste (notably, token notifications).
• Currently, Paste pages don't show tooltips on tokens.
• buildApplicationPage() stopped respecting pageObjects (which controls whether "this page has been updated" is shown). Restore that.
• Make pageObjects imply "clear notifications on this stuff".

Test Plan: Viewed a tokened Paste. Verified it cleared the notification and hovering over a token showed a tip.

Reviewers: btrahan, chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T3218

Differential Revision: https://secure.phabricator.com/D5971