Adjust Stapler parent module name and description

[Vlatombe]

This fixes a very small annoyance while building the project: both the aggregator and the core module have the same name, so the maven summary ended up like

[INFO] Reactor Summary for Stapler Parent 999999-SNAPSHOT:
[INFO]
[INFO] Stapler ............................................ SUCCESS [  0.367 s]
[INFO] Stapler ............................................ SUCCESS [  0.178 s]
[INFO] Stapler JSP module ................................. SUCCESS [  0.031 s]
[INFO] Stapler Jelly module ............................... SUCCESS [  0.041 s]
[INFO] Stapler Groovy module .............................. SUCCESS [  0.067 s]
[INFO] Stapler JRebel module .............................. SUCCESS [  0.030 s]
[INFO] ------------------------------------------------------------------------

which is not allowing to distinguish the 2 modules.

This updates the aggregator module name and description so that it is clearer.

Testing done

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