* Make theme able to load custom javascript
- Look for the field 'customScript' in editorTheme (settings.js)
- Add it to mustach context
- Load list on template side (index.mst)
* Add unit tests for customScripts
* Code review edits : generic behavior for theme.page.[css|scripts]
- Use the same way to share css and javascript files from a theme
- Allow string instead of array for theme.page.scripts
- Remove old customScript field