Django-pg-hll

Dependencies
1. Minimized dependencies
2. Removed psycopg2 from requirements.txt, so psycopg2 or psycopg2-binary can be installed

Features
1. Added HllExtension migration
2. Optimized dependencies

Compatibility
1. Fixed python 3.10 compatibility
2. Fixed django 3.2 compatibility in tests

Testing
1. Added docker testing infrastructure
2. Replaced custom hll installing with DockerHub image in GitHub Actions workflow
3. Replaced python 3.5 with python 3.10, django 2.0 with django 3.2, PostgreSQL 9.5 with PostgreSQL 13 in testing matrix

Features
1. Implemented configuration aggregations and transforms (`HllType`, `HllRegWidth`, `HllLog2M`, `HllExpthresh`, `HllSparseOn`)
2. Cardinality now returns `FloatField` instead of `IntegerField` as native field does
3. `HllField` parameters changed behavior: instead of hardcoding default values, it now bypasses defaults generation to database layer

Bug fixes
1. Fixed ability to pass parameters to `HllEmpty(...)` function

Testing
1. Refactoring of some tests
2. Added tests on hll fields comparison (`filter`/`exclude`)

Back incompatible changes
1. Cardinality functions no return results as `FloatField` instead of `IntegerField`
2. Moved `HllField` transforms to separate file (from `django_pg_hll.fields` to `django_pg_hll.transforms`)
3. `HllField` parameters changed behavior: instead of hardcoding default values, it now bypasses defaults generation to database layer

Bug fixes
Bug fixes in parametrized `HllField` creation by markallanson

Features
Added `CardinalitySum` function

Features
1) Added ability to save HllField value, got from database