Improve status email notification

This idea behind this PR is to improve the status email notification by adding a description of the changed metadata in the template mail. It is able to fetch some indexed fields related to the MD, so that the actual sent mail would look like:

```
Subject: My GeoNetwork catalogue / Metadata Workflow / Metadata record(s)
        Approved by admin admin (pierre.mauduit@example.com)
        (2014-04-16T13:37:19)

Change log message: No information

Metadatas concerned by this change are the following:
* title1 ()
* Pmauduit test 2 (the second test)


Records are available from the following URL:
http://localhost:8080/geonetwork/srv/eng/../../?s_E__status=2&s_E__statusChangeD
+ate=2014-04-16T13:37:19&s_search
```
By default, the format is the following (see strings.xml in the english version):
```
	<statusMetadataDetails>* {{title}} ({{altTitle}})</statusMetadataDetails>
```

It is possible to use any available indexed fields (`uuid`, ...).

The PR also fixes a bug with batch status update (a test had to be reversed, or else considering every existing MD as not found).