fix(cli): upgrade clean-webpack-plugin and change plugin require stat…

[danielkoch]

…ement

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] The commit message follows our guidelines: link tbd.
• [x] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] tooling / infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

clean-webpack-plugin is now available in v3

Issue Number: #65

What is the new behavior?

The cli and webpage installs clean-webpack-plugin in v3 but with v3 usage.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[jantimon]

We should rebase those changes once #72 are merged