Improve Windows start menu shortcuts (#2)

This is a replacement for PR #2631.

* Create Windows start menu shortcuts with better names.
* Add shortcuts for IPython Notebook and online documentation.
* Add icons for IPython console and notebook.
* Apply PEP8 to ipython_win_post_install.py.
* Tested on win32-py2.7, win-amd64-py2.7, win-amd64-py3.3, Windows 8.