Add metadata extractor for neo4j

[ravisuhag]

Deliverables

• [ ] add unit tests
• [ ] add extractor
• [ ] add README.md in plugins/extractors/neo4j, defining output
• [ ] register your extractor plugins/extractors/populate.go
• [ ] add extractor the extractor list in docs/reference/extractor.md

Output must contain a Table

Explore the Table Data Model and add as many features as possible.

Table

Field	Sample Value
urn	my_database.my_table
name	my_table
source	neo4j
description	table description
schema	[][Column]

Column

Field	Sample Value
name	total_price
description	item's total price
data_type	decimal