New Python language contrib, various fixes

New contribution layer

• python is now a contrib which can be found in contrib/lang/python. To use it you have to add python to your dotspacemacs-packages variable in your ~/.spacemacs.
  • anaconda-mode is now used for code navigation, documentation lookup and completion
  • ac-anaconda back end for auto-complete

Thanks to danielwuz!

New key binding

• <SPC> f e d opens your ~/.spacemacs dotfile (thanks to ralesi)

Fixes

• Fix emacs and emacs-debug-init functions on Windows (thanks to ralesi)
• Fix a remaining bug in automatic orphan packages deletion algorithm