Missing translations and escape

This PR fixes the following issues:

If a translation key is missing in some language, no input box was displayed. Now, an empty inut field is displayed in such cases
If the key contains html code, it would have been interpreted by the browser and not displayed correctly. Now, it will be escaped.
If the value contained quotes, the generated html for the input field is broken - the quotes need to be escaped so that the value is fully displayed inside the input field. Note: Only the quotes are escaped, nothing else - so it's still possible to have some html code for the values.

rasteiner / kirbytranslations