fix: applied translateDefaultValue to SectionSettings

[lukhong]

Previous PR #127 broke the behavior of textSetting that was showing nothing properly when the defaultValue was not specified. To restore that break, I've added translateDefaultValue() to SectionSettings to handle only the case of using locales.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [x] I have read the CONTRIBUTING document
• [ ] My code follows the code style of this project (hint: install an xo editor plugin)
• [x] Any required documentation has been added
• [ ] I have added tests to cover my changes

[lukhong]

@bflorian Applied your review and I just changed the target class to SectionSettings which has defaultValue originally.