Use the proper scope for headless param

(Scope(Java::Install[default-jre])) Could not look up qualified variable java::bool_headless; class java has not been evaluated at .../modules/java/manifests/install.pp:63
Merge pull request #6 from sathieu/for_upstream

Use the proper scope for headless param
Allow java::install where package is not empty

Default selector was for $book_jdk rather than for $package.
Merge pull request #7 from buildcom/master

Allow java::install where package is not empty
Release v2.0.4