Sets of Tags and Links now sort correctly

This was the straw that broke the camel's back, and forced me to begin
pushing Context down from the top.  (Since sorting Links requires
follow(), which requires Context.)  I believe this will become ever-more
common from here on.

Pulled Context and TypedValue out of the QLParser file -- that file had
become *way* too central to way too much code, and it was causing a
stupidly large number of recompiles.
Added edit fallbacks

If the requester can't edit, we shouldn't be displaying edit controls.
So _edit now falls back to simply rendering the property in this case.

Also, added _editOrElse, so you can specify in more detail what you'd
like to show if the requester can't edit this.

Added a little _editOrElse to EmailMessage, so it displays appropriately
to the public.
Release 0.3.13