source-to-source compiling of a DSL with Spoon

@andrewbwogi is interested in having a DSL extending Java which would be compiled source-to-source before compilation to bytecode with javac.

The source-to-source automated compilation is a solved problem, this would be done with https://github.com/SpoonLabs/spoon-maven-plugin

Now about the DSL, there are 3 options:

1. An annotation-based DSL with compile-time processing, this is easy, see chapter 3.4 of [Spoon: A Library for Implementing Analyses and Transformations of Java Source Code](https://hal.inria.fr/hal-01078532/file/article.pdf)
1. An embedded DSL with source-to-source compilation. This seems perfectly doable with Spoon but I don't have a concrete pointer on the top of my head
1. A syntactic Java extension. This requires some parsing that is out of the scope of Spoon. Note that [JastAdd](https://bitbucket.org/jastadd/jastadd2) is an option for this but not integrated with the Spoon analysis and transformation engine.

Any pointer on this @combemale, @jurgenvinju, @gorelhedin?