title: loadUpdateData in liquibase, select only some columns from csv
body: <p>Assume having the following csv:</p>
  
  <pre><code>a,b,c
  1,2,3
  </code></pre>
  
  <p>where a,b,c are column names and 1,2,3 are values.
  Is it possible to load only columns a,b?</p>
  
  <pre><code>&lt;loadUpdateData tableName="TABLE" 
              file="file.csv"
              primaryKey="a"&gt;     
              &lt;column name="a" header="a"/&gt;
              &lt;column name="b" header="b"/&gt;
  &lt;/loadUpdateData&gt;
  </code></pre>
  
  <p>This will generate an SQL error, because it will try to insert column c.
  I am using MySQL.</p>