Make the SSH port configurable

### Context
The plugin uses default port number when calling ssh commands

### Description
Now, it is possible to configure the port number.

Example in pom.xml
```xml
           <plugin>
                <groupId>net.codjo.maven.mojo</groupId>
                <artifactId>maven-test-release-plugin</artifactId>
                <configuration>
                    <serverMainClass>${serverMainClass}</serverMainClass>
                    <sleepAfterLocalStart>5</sleepAfterLocalStart>
					<!-- Ajout du paramétrage du port -->
                    <serverPort>2222</serverPort>
                    <server>
                    .....
           </plugin>
```