Thanks for the PR!

Feedback:

• an integration test fails with png format failed for following icons /home/travis/build/piwik/piwik/plugins/CoreHome/images/favicon.ico. Would it be possible to make the favicon PNG format?

I found this comment. Is it still relevant?

I'd say it's still relevant, but maybe the code below won't be useful / executed anymore as you seem to have converted all icons away from gif? If that's the case you could maybe try remove the code (or we can leave it as a fail safe in case icons in gif are later added)

an integration test fails with png format failed for following icons /home/travis/build/piwik/piwik/plugins/CoreHome/images/favicon.ico. Would it be possible to make the favicon PNG format?

What is the reason behind having a wrong file extension for png files and as a result sending the wrong mime type to the browser.
If you want to have a png favicon, we could add two icons (16px and 32px) and reference them as png. (As realfavicongenerator.net does it)

<link rel="icon" type="image/png" href="/plugins/CoreHome/images/favicon-32x32.png" sizes="32x32">
<link rel="icon" type="image/png" href="/plugins/CoreHome/images/favicon-16x16.png" sizes="16x16">

I'd say it's still relevant, but maybe the code below won't be useful / executed anymore as you seem to have converted all icons away from gif? If that's the case you could maybe try remove the code (or we can leave it as a fail safe in case icons in gif are later added)

I'd just keep it there.

If you want to have a png favicon, we could add two icons (16px and 32px) and reference them as png. (As realfavicongenerator.net does it)

Would be great to do remove our favicon.ico completely and do it properly with png files as you suggest 👍

@sgiehl you are right, I forgot about this possibility.
It gets even more complicated because chrome (also opera and chrome mobile) prefer ico favicons over png, if it has a higher resolution (mine includes 16,32,48,64px)
Safari (desktop always preferes the ico, even if it is smaller.
And the "old" Android Browser always picks the last defined icon.
http://caniuse.com/#feat=link-icon-png

I assume there is no way to generate multisize ico files in Piwik, so maybe it's really best to drop the .ico so it can't interfere with the custom favicon. (Which would have to be rewritten to generate the correct png files).

Could the project from @chrisbliss18 be of help here?
https://github.com/chrisbliss18/php-ico

I'll update the integration test so it does not check the format of favicon.ico. Merging now, Thanks @Findus23 for the PR!