Clean make

The various Makefile need some love. So, a new recipe `full` can be used to build programs from examples and contrib.

The `clean` recipe is also updated to work and clean stuff.

However, some questions:

1. Should the `clean` recipe clean the binaries? I did not fine a definitive answer on the Internet. 
2. Should the binaries be .gitignored?

Note: In a near future, Jenkins may also check that all the Makefile, and their `clean` work as expected.