generate:component script improvements

I ran across a few places where we could improve the generate component plop script, so I am capturing them here.

Storybook Template ➡ !1543 (merged)

Include scaffolding for props and data additions.

Import Paths ➡ !1551 (merged)

A number of path resolution issues needed to be fixed manually after generating a component.

See details.

In src/scss/components.scss:

@import '../componentssrc/components/base/combobox/combobox';

should be

@import '../components/base/combobox/combobox';

In /documentation/components_documentation.js

export { default as GlComboboxDocumentation } from '../src/componentssrc/components/base/combobox/combobox.documentation';

should be

export { default as GlComboboxDocumentation } from '../src/components/base/combobox/combobox.documentation';

In index.js

export { default as GlCombobox } from './src/componentssrc/components/base/combobox/combobox.vue';

should be

export { default as GlCombobox } from './src/components/base/combobox/combobox.vue';

In *.stories.js

'../../../../../documentation/documented_stories'

should be

'../../../../documentation/documented_stories'

Documentation Notes in componentName.md ➡ !1554 (merged)

Replace https://design.gitlab.com/components/ with https://design.gitlab.com/components/status, since the original link returns a 403.