title: Split a column of values delimited by colons into separate columns for each value
body: <p>I have a table of stings and numbers as below:</p>
  
  <pre><code>           V1                  V2
  1  GT:AD:DP:GQ:PL  0/1:10,45:55:70:106,0,70
  2  GT:AD:DP:GQ:PL  1/1:2,42:44:16:288,16,0
  3  GT:AD:DP:GQ:PL  1/1:3,37:40:14:147,14,0
  4  GT:AD:DP:GQ:PL  0/1:7,50:57:55:250,0,55
  </code></pre>
  
  <p>For vector <code>V2</code>, I would like to split the ':'- delimited (colon-delimited) values into separate columns for each value, <em>e.g.</em>:</p>
  
  <pre><code>   V1              V2   V3     V4  V5  V6
  1  GT:AD:DP:GQ:PL  0/1  10,45  55  70  106,0,70
  </code></pre>