index: Cleanup html and translations

[TrimmingFool]

• lang: Replace deprecated document.write

  • "Use of the document.write() method is strongly discouraged.", see: https://developer.mozilla.org/en-US/docs/Web/API/Document/write

• index: Remove IE9 script js/excanvas.js

  • Dropping support for the Internet Explorer since it has been deprecated by Microsoft

• index: Use html standard mode

  • This seems to be more accurate since no XHTML specific features are used and it is index.html and not index.xhtml

• translation: Clarify label size setting

  • I kept the existing translations

[stickz]

LGTM! We'll be able to confirm functionality when cloning the develop branch.