Prepare for Java 9

[twasyl]

As Java 9 is feature complete, SlideshowFX should prepare for Java 9.

Supporting Java 9 will require the following tasks:

• convert all modules to Java 9 modules: this mean creating all module-info.java files for modules
• take care of dependencies in order to still be able to provide the same features in the application
• evaluate how OSGi support could be dropped in profit of Java 9 services. For this we could maybe use the ServiceLoader
• if OSGi support is dropped we should take care of plugins versioning

In the first step, we should ensure the application is compiling properly, without plugins.
Then, we should be able to start plugins without taking care of the versioning.
Finally, the plugins should be versioned and the application should always load the most recent version of a plugin.