synchronize release binaries & announcements

[azrdev]

In https://sourceforge.net/p/auber/feature-requests/154/ I was told current binary releases were built with Qt5. When checking this, I noticed the builds on github differ from those on sourceforge:
github has separate 32 and 64bit builds and different python versions, whereas sourceforge does not tell about the bitness nor the included python version, but provides a download without python.
Looking at Qt versions: Sourceforge windows releases (at least tulip-5.1.0_x64_setup.exe and tulip-5.1.0_x64_no_python_setup.exe) are built with the obsolete Qt4, from github I get a tulip-5.1.0_x64_python36_setup.exe built with Qt5.

I think this situation warrants improvement:

1. Name the files according to their contents, i.e. bitness, Qt version, python version
2. Serve the same binaries from both sources, and/or get rid of one (sourceforge, probably) entirely
   • Currently it is not clear which download source should be used, the old website references sourceforge, as does the text of the github release, while in above issue on sourceforge I was told "Tulip development is now hosted on GitHub", and as explained for Qt5 builds I have to go to github
3. Eventually we should drop Qt4 and python2 (and maybe 32bit too) because they are superseded and not developed anymore. That many different tulip builds also have a higher potential for bugs found in one version, but not the other

[p-mary]

All Tulip downloadable binaries are now built with Qt5, and they are hosted on SourceForge.