Mode 1729 - Updated the AS7 kit to support federation

The basic schema which allows external sources to be defined inside of AS7 looks similar to the following:

```
 <external-sources>
    <source name="filesystem" classname="org.modeshape.connector.filesystem.FileSystemConnector"
                            directoryPath="${jboss.server.data.dir}" cacheTtlSeconds="1" readonly="true">
       <projection>default:/projection1 => /</projection>
       <projection>other:/projection1 => /</projection>
    </source>
 </external-sources>
```
The subsystem implementation approach is similar to the sequencers and text extractors.

To validate the functionality, a new set of _FederationIntegrationTests_ were added and the configuration updated with a federated repository which has 2 sources linked: a file system source and an git source.