Download.qt.io minor adjustments

Download.qt.io is a bit outdated in relation to other websites (cohesion, accuracy) and needs some minor adjustments to better enhance the feeling that this website is part of Qt. The amount of sessions is quite high and it would be good to better enable the movement of these sessions to our main domain and other domains (or whatever the user sees fit).

1. Change name "Qt Downloads" -> "Qt Community Download Server". New logo attached. Remove the text link next to the logo and only include the logo.
   1. In addition, change the Page title from "Index of /" to "Qt Community Download Server"
2. Navigation changes:

1. 1. Qt Home -> Qt Official Website
   2. Bug Tracker -> Bug Reports
   3. Code Review (no changes)
   4. Planet Qt -> Qt Blog (https://qt.io/blog)
   5. Get Extensions (no changes)
2. Remove ”For Qt Downloads, please visit qt.io/download” from footer
3. Include SSL certification (http -> https)
4. Insert a short description below header about what this page is all about. Suggestion:
   1. Welcome to Qt Community Download Server! From here you can easily download Qt related content. If you would like to read more about contribution via Open Source and obligations, please follow this link(insert link to https://www.qt.io/download-open-source#obligations).