title: Return array of values when querying single column instead of array of objects
body: <p>When using the query builder in typeorm I do a select of a single column and I would like to get an array of values (In my particular case it would be an array of strings) but instead I get an array of objects where the key is the column name and the value is the row value.</p>
  <p>For example the code:</p>
  <pre><code>this.createQueryBuilder('subscriptions')
    .select('id')
    .getRawMany()
  </code></pre>
  <p>Would return something like:</p>
  <pre><code>[{id:1},{id:2},{id:3}]
  </code></pre>
  <p>Instead of a simple array like <code>[1,2,3]</code></p>
  <p>Is there any way to obtain this array from the query? or the only way is to map the result of the query to extract the value?</p>