GH-2244: Unit tests for Ghostery Dawn Intro Hub

[benstrumeyer]

• Have you followed the guidelines in CONTRIBUTING.md?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you added an explanation of what your changes do?
• Does your submission pass tests?
• Did you lint your code prior to submission?

• Add tests for WelcomeView, LoginFormContainer, LoginFormView, CreateAccountView, BlockSettingsView, ChoosePlanView, SuccessView, and StepProgressBar
• Did not add test for ChooseDefaultSearchView
• Add tests for corresponding actions and reducers
• Update index of StepNavigation to be a string from OnboardingConstants
• Update PropTypes
• Add license to sass files
• Remove withRouter() from Step1_CreateAccountView since buildReduxHOC already has it
• Fix bug on ChoosePlanView where cards were not shown for a basic user
• Update copyright year for the intro hub

[wlycdgr]

A few cleanup-type comments and a couple spots where the reducer tests MAY give false reassurance