Feature/169

[xiaoweiguang]

• Commented out 'react-axe', which conflict with 'i18next'.
• Changed .env file to use connection string instead of environment variables.
• Added custom back button to top of the header using call back function.
• Cleaned ESLint warnings.
• Cleaned React prop validation errors.

[sugaroverflow]

Merged automatically - thanks for your work on this!