Fix description on how import-package manifests are generated

The documentation at http://jackrabbit.apache.org/filevault-package-maven-plugin/import_package.html for HTL scripts should it make more obvious that the phase of the validate goal needs to be overwritten to let the maven-compiler-plugin pick up those sources as well (see SLING-7274). Also now version 1.1.0 of the htl-maven-plugin has been released.