WinPython web page cleanups #572

A few suggestions for cleaning up the various web pages related to WinPython - the current state of these (outdated/poorly documented) is discouraging uptake of WinPython.

This is all about simplification for new users.

1 - Replace entire contents http://winpython.sourceforge.net/ with a web redirect to http://winpython.github.io/, or if that's technically difficult, then leave only the first line ("Since September 2011...") and delete the rest.

All this info should be in a single place, not spread across both SourceForge and GitHub. Having the remainder of that page live is confusing for new users - anything of value should be moved to the appropriate place on GitHub (if not already there) to keep it all in one place.

2 - Not clear why both http://winpython.github.io/ and https://github.com/winpython exist. They should be combined into one single page, with the deprecated one pointing to the other.

3 - Remove all references to SourceForge from the main GitHub page. Downloads should be listed directly on the main GitHub page, not redirected to SourceForge (it's fine of course if the files are actually stored on SourceForge, but users shouldn't need to see that).

4 - Add clear explanation of the differences between Qt5 and Zero versions, why one might choose one vs. the other.

5 - Explain the purpose and differences between the 4 sites linked currently at https://github.com/winpython.

Right now, these exist without any useful description of what they are and why they're useful (or not).

There are other issues, but these are the biggest high-level ones, and would be a great start.

(Yes, I know this stuff is a bother, but it's really critical to onboarding new users.)