UTF-8 support for properties files editing in studio

Currenly, Studio does not support UTF-8 editing of properties files.
This ends up languages like Japanese being displayed with weird characters. (see propertiesEditing.png).

A solution would be to edit locally the properties files and upload them to Studio but that takes more time than directly editing in the Resources screen.

TODO:

• Allow UTF-8 encoded files edition in properties files

HOW TO DEMO / TEST:

• Upload and try to online edit a file containing Japanese / cyrillic / hebrew / chinese characters