Allow column selector to work on multiple columns

[vivekmiyani]

@vedmack Sorry for late reply, Let me explain a bit regarding this PR.

When we use column selector, see below columns:

...
<tr>
  <th data-column-type="dropdown">Column 1</h3>
  <th data-column-type="checkbox">Column 2</th>
  <th data-column-type="dropdown">Column 3</th>
</tr>
....

Expected Behaviour: data-column-type="dropdown" selector should work on 2 columns (i.e. Column 1, Column 3).

Actual Behaviour: data-column-type="dropdown" selector is only working for the first one (i.e. Column 1).

[vedmack]

Hi

In case it's still relevant, you will need to provide a jsfiddle (or similar) test page so I can see it in action...