Moved the release tasks back to Ant:

- we want to run it as a separate step any ways, so lets leave the
  existing Ant script as-is and not try to cram it in a single
  Gradle build process;
- minor fixes.
Migrated gradle build to new version:

- cherry picked the new gradle build from the Bnd project;
- removed the obsolete gradle files from the old version;
- added a minor hack to allow extra source paths to be defined,
  although Bnd this does not support out-of-the-box.
Latest version of LibTDL.