Added support for temp dbs (#88)

[AndySakov]

Added util functions to manage temp databases (create and delete) and integrated them as methods on the Neogma class.

• Copied over the functions from the @neo4j-labs/temp-dbs repo and ported them to typescript.
• Integrated the functions into the Neogma class and removed the driver.close() calls in the functions in favor of the global driver manager.
• Added tests to make sure the intended behaviour was successfully implemented.