Adding support for rows column

Adding rows column for creating multi-line text boxes.

More info:

>Beginning with ODK Collect 1.3, if you want a string field that always displays an edit box with more than one row of text, even if the field's text value could fit on one row, you can specify a rows attribute within the <input> tag. I.e.,
```xml
  <input ref="my_string" rows="5">
    <label>string widget</label>
    <hint>can be short or very long</hint>
  </input>
```
The above declaration will present a 5-line edit box that will grow larger if necessary but which will never display smaller.

Also removing xlsform_spec_test.xls which has been superseded by xlsform_spec_test.xlsx

@ukanga