title: R data.table split a row into multiple rows based on string values
body: <p>I have a data.table like this:</p>
  
  <pre><code>dt &lt;- data.table("title"=c("First Title", "Second Title", "Third Title", "Fourth Title"), 
                   "sha"=c("12345", "2345; 66543; 33423", "22222; 12345678;", "666662345; 444"))
  </code></pre>
  
  <p>How can I get this:</p>
  
  <pre><code>      title                sha
  1:  First Title           12345
  2: Second Title           2345 
  3: Second Title           66543
  4: Second Title           33423
  5:  Third Title           22222
  6:  Third Title           12345678
  7: Fourth Title           666662345
  8: Fourth Title           444
  </code></pre>
  
  <p>Thanks in advance!</p>