Add support for automatic module name

[dmlloyd]

Fixes #520 for the 4.x branch.

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[slachiewicz]

@desruisseaux aby comment on this?

[desruisseaux]

My initial comment was on #520. There are also useful replies below it. I see two aspects to consider:

A first aspect is that this feature can be seen as a shortcut making possible to write in 3 lines of pom.xml code what currently requires 7 lines. However, I think that having many ways to do the same thing can be a source of confusion. If configuring the automatic module name in a poml.xml file was difficult, it would be a strong argument in favour of an alternative way. But if (except for the second aspect below) it only saves 4 lines of code, I tend to value more the consistency aspect even at the cost of a little bit of verbosity.

A second aspect is that apparently, the current way is difficult if we want to set the automatic module name through a property on the command-line. But I agree with @elharo comment that module name should be part of the versioned code, and therefore be written in the pom.xml if it cannot be written in module-info.java. If nevertheless there is really a strong demand for setting the module name from the command line, I would be more in favour of investigating why the current approach does not work and if it could be fixed.