Dgraphpandas

- Implemented Type Writer (pre-frame uses the existing schema generation)
- Added Docs for Type Generation
- Updated cli to expose `types` operation
- Updated Samples
- Added tests for main cli

- Implemented Schema Generation from Config
- For a given configuration, generate a schema to be applied to dgraph live loader
- Updated unit testing to use pytest
- Updated Documentation
- Corrected Boolean type mappings

- Corrected Linting / Style errors reported by Codacy
- Added Testing Coverage Report
- Updated Documentation

- Centralized logic into `to_rdf` and exposed on package level
- Added `get_config` method
- Updated Assertion helper logic to have no coverage
- Updated `__main__` to use `to_rdf`

- Added option for custom predicate and object in vertical transform
- Updated Documentation

- Added automatic `_id` edge convention derivation
- Added additional types to rdf type mapping
- Updated Documentation