[MPLUGIN-486] display leaf parameters if a parameter is a complex object

**[Ernst Reissner](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=ernstreissner)** opened **[MPLUGIN-486](https://issues.apache.org/jira/browse/MPLUGIN-486?redirect=false)** and commented

In my configuration I have a `@Parameter` named `settings`
which is an object with fields again `@Parameters`.
This is because I have a lot of parameters and this is a way to structure the parameters.

The problem is, that `mvn latex:help -Ddetail=true`
(`latex-maven-plugin` is my plugin) tells me only that `settings` is a parameter
without displaying the parameters nested inside.

Maybe I dont use this plugin properly, but then maybe some improvement in the documentation would be helpful.

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No further details from [MPLUGIN-486](https://issues.apache.org/jira/browse/MPLUGIN-486?redirect=false)