title: Spark dataframe string to month
body: <p>I have a dataframe where one column <code>orddate</code> as string, and I want to extract months from the <code>orddate</code>, make a new column with <code>month</code> name on new df.</p>
  
  <pre class="lang-none prettyprint-override"><code>|orddate|
  |12/1/10 9:37| 
  |20/3/10 10:37| 
  |09/8/14 4:56| 
  |30/12/11 12:13| 
  |24/5/10 7:27|
  </code></pre>
  
  <p>convert to </p>
  
  <pre class="lang-none prettyprint-override"><code>|orddate| month |
  |12/1/10 9:37| january|
  |20/3/10 10:37| march |
  |09/8/14 4:56| august |
  |30/12/11 12:13| december |
  |24/5/10 7:27| may |
  </code></pre>