Add support for additional targets using plugin configuration

[lucapino]

Add support for adding additional target configuration using plugin configuration
The proposed configuration could be like this:

<plugin>
    <groupId>com.hcl.security</groupId>
    <artifactId>appscan-maven-plugin</artifactId>
    <version>1.0.14-SNAPSHOT</version>
    <configuration>
        <additionalTargets>
            <target>
                <targetFile> ... </targetFile>
                <properties>
                    <src_root> ... </src_root>
                </properties>
                <exclusionPatterns>
                    <exclude> ... </exclude>
                </exclusionPatterns>
                <inclusionPatterns>
                    <include> ... </include>
                </inclusionPatterns>
            </target>
            ...
        </additionalTargets>
    </configuration>
</plugin>