fixing typo and code cleanup

* "unbinded" typo are changed to unbound (shame on me)

* tasks definition are now cleaner :

   * less use of << operator.
   * using more the task inheritance mechanism with configuration
   closure.
   * 'generateUnbindedJar' attribute is now gone from the DSL
   extension, setting 'unboundJarName' will imply the build of a
   jar containing unbound classes

Change-Id: Ib682fac7f0f07dc6ad16807a820fbb3e38d8f84a