Docs - Renaming docs for "components" to "fragments"

[rtablada]

Currently in the docs there is a section for "Components" which is confusing when someone may be looking for how to test @ember/components in their application. It think it would make sense to rename this section to fragments or maybe "organizing and sharing functionality".

The emphasis for this is because with the addition of #444 and documentation around it would add official docs for how to use this addon in integration tests to test actual Ember Components which then would cause confusion between the current section (which is more about organization) vs the integration test usage.

[ro0gr]

I think it's more about "definitions". components are page object instances while defs aren't.

I like the fragments name. However, I think they should provide a way to compose an instance from multiple fragments with a well specified merge behavior.

The best we currently can do with definitions is:

const i = create(
  Object.assign({}, def1, def2, {
    scope
  })
);

which is far from being ideal.