title: BigDecimal += (add and assign) ...How to do this?
body: <p>I can't seem to locate an 'add and assign' method in the BigDecimal class.</p>
  
  <p>Is there a method for this?</p>
  
  <p>In case you don't understand my question I'm trying to do this:</p>
  
  <p><code>a += b;</code></p>
  
  <p>but I'm trying to do it with BigDecimals</p>