Recursively check whether GraphQLQueryTree.name is part of EntityMetadata.propertiesMap

[Migushthe2nd]

Fixes #11

This makes it so that the recursive query builder also checks for all sub-fields whether the graphql field is actually part of the entity's propertiesMap. Line was taken from: https://github.com/wesleyyoung/perch-query-builder/blob/3b4bebfc04a8909420e0cad779e0294403bcca7e/src/classes/PerchQueryBuilder.ts#L26