Clean up and migrate from ts-krinkle-I18N to tool-labs/intuition

* Rename display name from "CVN SimpleOverlay" to "CVN Overlay".
* Migrate localisation backend from toolserver.org/~krinkle/I18N.php
  to tools.wmflabs.org/intuition/
* Messages added in https://github.com/Krinkle/intuition/commit/3292c843560ef19c3c098d8de49188cc507b2484
* Use mw.util.getUrl instead of deprecated mw.util.wikiGetlink.
* Drop support for SVG PNG fallback.
* Drop function name prefix 'cvnSO_'.
* Change internal id prefixes from cvn-so to cvn-overlay.