Verify proper behaviour of QWebEngine for our html

[baudren]

We should make a small proof of concept to check that the QWebEngine can indeed be a significant improvement over the QWebView. Among other things, we need to be sure that

• [x] it handles multiple css files
• [x] it manages bootstrap plus custom themes and still use monospaced fonts
• [x] it handles js properly (so far we are not using much, but it may change).

[baudren]

As a first step, I checked that Chromium (on windows) handles local files well - it reads perfectly our currently generated html files (so with just one css). Incidentally, it does a better job than Firefox at this (Firefox does not interpret css when reading local file).

Since QWebEngine is using Chromium, this bides well for our purpose.

[egolus]

just to clear things up: Firefox handles css in local files, the path to our local css is just in a format that firefox doesn't recognize. If you correct the path (IIRC adding http:// is enough) the css is handled correctly

[baudren]

Thanks to @egolus try outs, we now know that everything works, so all is good and the refactoring will bring really nice things to the table. Thanks for the work!