Use SVG favicon instead of ICO

[Lineflyer]

The old school favicon.ico should be replaced by a SVG.

How to: https://wiki.selfhtml.org/wiki/Grafik/Favicon#SVG-Favicons

[ztNFny]

which icon shape do we want to use as primary? On Android it's controlled by the users setting, but for images like on the website we have to decide.

Or maybe it's a "it depends"? For the logo on the site I like round, but for favicon both round and square work just fine imho.

[Lineflyer]

For the classic favicon.ico I used the square, so I suggest the square. The round on the page looks better IMHO.

@ztNFny Did you see: For the cgeo website I opened the same issue.

[ztNFny]

I'll upload square SVGs for both project + round for WYG

[ztNFny]

I added them to the main repo cgeo/WhereYouGo#361