[jvm] Add an Automatic Module Name for XGBoost

I am trying to use XGBoost from a Java project, but it's difficult to use along with `module-info.java`.   The reason is that there is no module name for XGBoost, and the automatically generated one doesn't work with the Jar name.   

Specifically, Java can't derive the name from `xgboost4j_2.13-3.1.1.jar`.  Normally it would be able to, but the `2.13`, the Scala version, makes it have this error:

```
Tue Nov 04 11:01:11 $ jar --describe-module --file xgboost4j_2.13-3.1.1.jar
Unable to derive module descriptor for: xgboost4j_2.13-3.1.1.jar
xgboost4j.2.13: Invalid module name: '2' is not a Java identifier
```

I believe the correct way to fix this is to add a MANIFEST.MF Entry like they did here: https://github.com/oshi/oshi/issues/1243

I am not familiar enough with Maven to know how to add it [but here is a try](https://github.com/carl-mastrangelo/xgboost/commit/cd902b5569b94e52d69d6126c7f43ea9936aa4ef).   This [blog post](http://branchandbound.net/blog/java/2017/12/automatic-module-name/) describes how as well.

[]