title: New column in the start of a data table
body: <p>I can add a new column to a data.table like this:</p>
  
  <pre><code>DT = data.table(A=sample(3, 10, TRUE), 
           B=sample(letters[1:3], 10, TRUE), C=sample(10))
  
  DT[, new:=1:10]
  </code></pre>
  
  <p>But is there a clever way to set it to the start of the data.table? - I know i can do it with setcolorder, but I would like to avoid that. </p>
  
  <pre><code>setcolorder(DT, c("new", "A", "B", "C"))
  </code></pre>