Fixed broken build system in broken webpack version.
Also updates module system to standardise on ES6 import/exports,
Especially since babel has changed it's 'default' logic for the old
module system.
For #939
- Adds way to check if current language is RTL via config system.
- Made TinyMCE default direction be based on current language text
direction.
- Fixed bullet points to be RTL compatible.
- Set page content body to have direction based on content.
