Fixes #3079

Break test target into smaller targets

- Add “make test” command to lint, test and report coverage
- Add pytest runner 
  - It automatically set up to use the correct Django settings module
  - Runs tests on all the available CPU, I was able to run all the test in total=~30sec using “make test” command.
  - It provides a cleaner error report, compared to DjangoTestRunner
- Coverage
  - Displayed the report on the terminal after the test finish
  - Disable reporting of coverage for test and migration files
  - Enable coverage reporting for the template files
  - “make test” generates HTML reports to quickly check the coverage of each file

- Add missing PHONY definition for `help`
- Add `lint` command to run both isort and flake8
- Add `style` command to run flake8
- Rename `fix` to `sort-fix` to fix the isort errors
- Remove exit code from `sort` as it hid errors and emits error codes anyway