Update the update policy some more
    
    - it turns out we have three freezes (post-branch, beta, final). The
      document described all three, but said we have only two.
    - various links are updated where pages have been moved
    - style is consistentized: e.g. SHOULD was boldface sometimes. Since
      it's already uppercase, making it boldface in addition is excessive.
    - rawhide/Rawhide → Rawhide
    - rebase/update → update
    - the rules for when an update is pushed to stable are completely rewritten.
      I *think* it's much easier to understand them now.
    - the semi-obsolete description of critpath packages is removed and
      replaced by a link to the description on the wiki, that also describes
      how to query the list.
    - "bodhi compose enablement" point is now called "Updates-testing Activation".
    - a TOC is inserted at the top, it helps to naviate the page.