Localization missing and causing errors

[KacperMadej]

Behaviour

If highcharts.editor.lang.he.js is being used class names are being translated, but in code those are hard-coded, so an error occurs.

Second issue is that it looks like most of the texts are not translated - there is a lot of bad localized string: texts all over the Editor.

Reproduction steps

1. download standalone from 0.3.0 release
2. download highcharts.editor.lang.he.js
3. edit standalone.html to load the lang file and set lang highed.setLang('he')
4. open the standalone.html and toggle to the customization tab

Editor version

0.3.0