Facilitate upgrade step code management for Maven based applications

[fabiocarvalho777]

Butterfly extensions that need to deal with upgrades of Maven based applications can get really complex, large and verbose if they have multiple upgrade steps, plus multiple application types and a hierarchy of upgrade steps.

In cases like this, managing these upgrade step classes is very error prone and time consuming. In addition to that, maintaining the transformation template automatic resolution logic makes the problem even worse.

In order to reduce this extension development and maintenance pain, the API and/or its internals need to be simplified and enhanced.

One option to achieve that is by creating a subclass of UpgradeStep specific to deal Maven based applications. And then, move from the extension to Butterfly most of the necessary code to tie the upgrade steps and to automatically resolve the transformation template.