Fix maven lifecycle-usage

[FibreFoX]

Before this changes, calling "jfx:jar"/"jfx:native" via CLI was mixing lifecycle and direct-call.
Now its possible to have this kind of configuration:

<plugin>
    <groupId>com.zenjava</groupId>
    <artifactId>javafx-maven-plugin</artifactId>
    <version>8.1.3-SNAPSHOT</version>
    <configuration>
        <updateExistingJar>true</updateExistingJar>

        <mainClass>javafx_and_proguard.MainApp</mainClass>
    </configuration>
    <executions>
        <execution>
            <id>create-jfxjar</id>
            <phase>package</phase>
            <goals>
                <goal>build-jar</goal>
            </goals>
        </execution>
        <execution>
            <id>create-native-mac</id>
            <phase>package</phase>
            <goals>
                <goal>build-native</goal>
            </goals>
            <configuration>
                <keyStoreAlias>example-user</keyStoreAlias>
                <keyStorePassword>example-password</keyStorePassword>
                <allPermissions>true</allPermissions>

                <bundler>mac.app</bundler>
            </configuration>
        </execution>
    </executions>
</plugin>

This allows to have encryption/obfruscation/etc. and javafx-maven-plugin within regular "mvn install" call.

Now this is possible to create javafx-jar/installer:

• mvn install (with configured phases)
• mvn jfx:jar
• mvn jfx:native

When having both mixed, configured executions are skipped.

(to mention it: Fixed license-header and removed deprecated preloader-field of native-mojo)

[FibreFoX]

the new goals for package-phase are these:

• build-jar
• build-native

[FibreFoX]

@maxd can you check this PR for me?

[FibreFoX]

This PR is ment to be a fix for these issues: #64 #65 #82

[maxd]

I have tested it right now. All works fine. Problem with duplicate build phases is solved. 👍