LICENCE_HEADER added
[Kernel] Multiple round init for plugins fix #27

The kernel can now offer multiple round for plugin initialization.
The init method should return weither it is actually initialized.
If not, the kernel will add for another round, until a maximum round
number is reached. 

Please note that dependendent and required plugins are not pass as
argument after the first round.

see http://github.com/kametic/nuun-framework/issues/issue/27