[Dev] adding "triage status" to the summary view

[Alec Flett]

I've added a "triage status" column to the summary view and a 
"triageStatus" attribute to ContentItem, with a really basic display - 
i.e. right now it renders just as an editable string, and defaults to 
"now" but can also contain "later" and "done"

This is mostly a strawman so that we can start experimenting with 
different ways of dealing with triage. I'm hoping to get some help from 
Bryan next week to at least turn this into a combo-box. (Not because 
anyone has decided on a combo box but because the string attribute 
editor is really the wrong editor for this case!)

[Bryan: I tried using ChoiceAttributeEditor, which started to complain 
about the AE not having a 'presentationStyle' attribute, which lead my 
down a twisty road of things I don't understand.. ]

Alec