Initializes project to test the plugin.

Improves pom.xml to add some libraries and plugins
necessary to test the project and create test cases
to launch the plugin on some sample projects. There
is a test case to spoon a sample project, hello-world,
and 2 another test cases to spoon projects with
a custom configuration.
Adds test cases to test configuration builder.
Merge pull request #14 from GerardPaligot/init_test_env