Include relationship types in plan description.
Unify Expand{ByName/ById} pipes

Instead of building different pipes for relationship types that are known
at planning time and the ones that are not, we now lazily initialize fetch
the relationship type ids, and only ask to traverse by the types that
actually exist at the point in time when the query executes.
Merge pull request #3673 from pontusmelke/2.2-improved-plan-description

Improved plan description