Updated system requirements, DOM is required since 2.9
Merge branch '2.11' into 3.0
Contao 3 only supports Internet Explorer 8
Merge branch '3.0' into 3.1
Merge branch '3.1' into 3.1-ja.
Catch up to 08496d1d664aa265115c0f69463a04b0674e431f.
PHP version fix.