Splink-graph

From this release owardn, functions to be seperated logically in appropriate submodules:

eg


from splink_graph.cluster_metrics import x
from splink_graph.node_metrics import x
from splink_graph.edge_metrics import x


Also column names are more consistent.

- added more cluster statistics functions
- added custom fields to pandas udf functions
- added more tests

- linting
- diameter_radius_transitivity function added in order to get most important cluster statistics
from one pandas_udf function

v.0.2.1
- took out spectral clustering function for the time being (will reintroduce it properly)
- ran black formatting tool

- PANDAS_UDF Arrow-based functionality added
- Vectorised calculations

v.0.1.0