Locking Android screen orientation using AndroidManifest.xml's activity element (revised)

In #78, @richardPFisk proposed adding the ability to lock Android's screen orientation by modifying the AndroidManifest file.

```
<manifest>
  <application>
    <activity android:screenOrientation='portrait'>

    </activity>
  </application>
</manifest>
```

After he revised his pull request to use CoffeeScript and split out the included `phonegap:debug` feature into #82 (which has now been merged into **master**), I added some documentation for the feature and set the test screenOrientation to "portrait".

I now consider the feature ready for release.