Custom directives run AFTER data injection

[gpaluk]

Custom directives run after the data has been injected into the database and therefore unfit for the most obvious use-cases. For example, annotating a field with validation prior to being inserted into the database is not possible. The only alternative is to use a custom resolver for almost every field. This poses the problem that all graphql schema declarations would need to be annotated with neo4j_ignore thus rendering makeAugmentedSchema almost obsolete.

[michaeldgraham]

#608