Introduced better AJAX editing

Added the new setProperty2 entry point, which may entirely replace
setProperty since it is far more powerful.  This is basically a shallow
front end to doEditInternal, so it doesn't cheat like the old
setProperty did.

Changed the thing.html updateValue() handler to use setProperty2.  We
now use jQuery's serialization capability to serialize the values for
the form, and mock up the rest of the form.
Tag Sets starting to work in the general case

I suspect it's still buggy, but you can now modify Sets of Tags and
Links from normal Thing windows.
Prevent over-eager live updating of Tag Sets

It's a crude state variable, but it seems to work as expected.
Main Email display is now highly editable

Not perfect yet -- the mechanism for displaying the controls is too
kludgy -- but it's a good start.

Text and Tag fields now auto-widen when they are displayed in a form.
Added _formLine method

Using this for the Email Message.  _formLine is a crude and unpretty but
reasonably effective input.  It also happens to be near-identical to
what the Editor does, so it's a step towards obviating away the
editThing page.