* Start Python Policy updates for Wheezy
    - Document current practice to not provide /usr/bin/python2
    - Strengthen warning aginst using /usr/bin/env python     
    - Update paths section for python2.7 and python3
    - Deprecate XB-Python-Version
    - Clarify use of {python:Provides}
    - Clarify that build-dependencies on -dev packages should not be used
      except when required