title: How to find the time difference between 2 date-times in Scala?
body: <p>I have a dataframe </p>
  
  <pre><code>+-----+----+----------+------------+----------+------------+
  |empId| lId|     date1|      time1 |  date2   |    time2   |
  +-----+----+----------+------------+----------+------------+
  | 1234|1212|2018-04-20|21:40:29.077|2018-04-20|22:40:29.077|
  | 1235|1212|2018-04-20|22:40:29.077|2018-04-21|00:40:29.077|
  +-----+----+----------+------------+----------+------------+
  </code></pre>
  
  <p>Need to find the time difference between the 2 date-times(in minutes) for each empId and save as a new column. 
  Required output :</p>
  
  <pre><code>    +-----+----+----------+------------+----------+------------+---------+
      |empId| lId|     date1|      time1 |  date2   |    time2   |TimeDiff |
      +-----+----+----------+------------+----------+------------+---------+
      | 1234|1212|2018-04-20|21:40:29.077|2018-04-20|22:40:29.077|60       |
      | 1235|1212|2018-04-20|22:40:29.077|2018-04-21|00:40:29.077|120      |
      +-----+----+----------+------------+----------+------------+---------+
  </code></pre>