Fixed #16205 -- Added beginner guide for windows.

This is mostly the work from https://code.djangoproject.com/attachment/ticket/16205/16205.diff
I have removed "Setting up ENV vars" as decided as Users must know this, instead just written to ensure that ENV vars have been set up.
Improved upon language at some places.
Added issues to `Common Pitfall`. If anything more can be added to ``common pitfalls``, I'll be glad to do it.

Also I think something needs to be done about https://code.djangoproject.com/wiki/WindowsInstall