Python interface

There are some differences to what the CC class used to be:
  * `vigra::TinyVector` is no longer exported (this is done in vigra)
  * the CC class is not exported for `float` anymore
  * messages to stdout were removed
  * `_import_array()` is no longer called during module init
  * label type is now `unsigned int` (`int` before)
  * CC class is now also templated with source type
  * `Roi` has new getter and setter methods for p and q (problem with `TinyVector` converters)
  * ~~removed `const` from sink `TinyVector`s for compatibility (they are returned by-value anyways)~~