Make StrictHostKeyChecking configurable

[sparsick]

As developer, I want to make the option StrictHostKeyChecking configurable. The default should be true.

[georgberky]

We have agreed on the following configuration format:

    <build>
        <plugins>
            <plugin>
                <groupId>${project.groupId}</groupId>
                <artifactId>${project.artifactId}</artifactId>
                <version>${project.version}</version>
                <configuration>
                    <gitProvider>JGIT</gitProvider>
                    <sshOptions>
                        <strictHostKeyChecking>false</strictHostKeyChecking>
                    </sshOptions>
                </configuration>
            </plugin>
        </plugins>
    </build>