Pykeadhcp

- Addresses issue 16
- Addresses issue 12
- Dhcp6 Parser for those who don't pay for premium hooks is now implemented with basic functionality, more functionality will come....
- Majority if not all models will now include the `user_context`, `comment` and `unknown_map_entry` as these are typically populated across all configs for shared-networks, subnets, reservations, etc...
- General pydantic model cleanup
- Dhcp6 Tests for the local parser, including PDPool exceptions
- Dhcp6 API config for CI testing
- CtrlAgent API config now includes TLS/SSL, docker test infrastructure needs to be updated to automatically generate this certificate for future tests to pass if other developers contribute
- Additional option on pytest conftest to disable SSL/TLS verification or point to an SSL/TLS CA bundle
- More work on Dockerfile for premium hooks, next few patches will provide better developer experience for those that have access to the premium hooks

Prerelease of v0.4.0 which supports Dhcp6 parsers, implements more tests, SSL/TLS support/verify and general model cleanup

- Implemented more functionality on Dhcp4Parser
- Implemented more tests
- Changed model variables that are lists to default empty list, to prevent .append() errors on NoneType
- Changed any API calls to `exclude_unset=True` to avoid API errors (eg. reservations must not be present when calling subnet4-add)

Daemon models have been implemented for the following:

Dhcp4
Dhcp6
CtrlAgent

Concept of Parsers have been introduced but only Dhcp4Parser has some examples in it, this is to provide similar functionality to interact with the configuration locally for those who do not pay for the Kea premium hooks and are unable to use commands like `subnet4-get` or `network6-add` as an example.