Upgrade Webpack to version 4 (#223)

[ghost]

Upgraded webpack to version 4

Description

Upgraded webpack and webpack related dependencies and added wepack 4 related properties in config objects.

Related Issue

babel-loader is not upgraded as it would require babel to babel 7 migration and that would require changing hot reloading configuration by dropping babel-preset-react-hmre package using react-hot-loader and that that can be worked on under another issue for HMR implementation.

Reviewers

@vpn1997

Types of changes

• 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)
• Other

Screenshots (if appropriate):

Checklist:

• My code follows the code style (modified PEP8) of this project.
• I have updated the documentation accordingly.
• The code has been tested locally.