Merge pull request #13: 4.0.0 version

- added full test coverage with standard unit tests
- NEW FUNCTIONALITY: added template repository manipulation class DomainConnectTemplates

Merge pull request #11 from Domain-Connect/feature/templatetestcases

Variable extraction for groups & bugfix on empty host from variable in pointsTo/target

Merge pull request #10: NEW FEATURE: REDIR301/302

NEW FEATURE: group IDs extraction from the template

BUGFIX: allow underscores in SRV host

NEW FEATURE: improved template validation

BUGFIX: fixed get_variable_names for python 3.8 compatibility

BUGFIX: fixed SRV validations

IMPROVEMENT: added more verbose errors