Remove irrelevant reference to a "security best practice"

This change includes three things:

1. Removing note about omitting version number due to "security best practices" as not including a version number is actually more [security through obscurity](https://en.wikipedia.org/wiki/Security_through_obscurity) rather than any real security.
2. Removed the irrelevant Stallman reference.
3. Syntax highlighting.
Use svg instead of png to get better image quality
Merge pull request #6460 from breadtk/patch-1

Removed a reference to a security "best practice"
Merge pull request #6461 from PeterDaveHello/patch-1

Use svg instead of png to get better image quality
Refs #6364, proper fix for json_encode error on some 5.3 versions of PHP. When decoding &nbsp; use UTF8 encoding so json_encode will not complain.
Removed the PclZip lib since it has moved to piwik/decompress
refs #6465 Allow 5.6 build to fail - note: we must find proper solution to
only notify Slack when the build status changes
refs #6281 - added missing search engine hosts for Ask and Zapmeta
fixes #6281 - added detection for findhurtig.dk and genieo.com
refs #5940 fix omnifixture creation was no longer possible
refs #4996 update ui test fixture
initiate ui tests again
Merge pull request #6467 from piwik/uiFixtureUpdate

Update UI test fixture
updated submodule
Merge branch 'master' of github.com:piwik/piwik
remove comment
wider plugin setting textarea
Merge branch 'master' of github.com:piwik/piwik
Fixes #6465 Tests failures with PHP 5.6