Added l10n for ZXing intent message box

that is shown if Barcode Scanner is not installed.

Original strings are
```JAVA
public static final String DEFAULT_TITLE   = "Install Barcode Scanner?";
public static final String DEFAULT_MESSAGE = "This application requires Barcode Scanner. Would you like to install it?";
public static final String DEFAULT_YES     = "Yes";
public static final String DEFAULT_NO      = "No";
```
keep previous indentation