DocBook transformation generates invalid XML

Generating DocBook output for the sample files included in distribution packages yields invalid XML.

For example, the output generated for `sequence.ditamap` in `docsrc/samples` via:

``` bash
dita -input sequence.ditamap -f docbook
```

generates a `sequence.xml` file that begins as follows:

``` xml
Working in the garage

Changing the oil in your car
```

The map's `@title` attribute (``) is placed as character data in the `` element followed by a self-closing `` tag, which triggers a validation error:

```
E [Xerces] Unexpected character data "Working in the garage".
The content of the parent element type is element only.
```

For valid XML, the map title should appear in the article ``:

``` xml
<article>
<title>Working in the garage

Changing the oil in your car
```