Set up Plugin architecture (modules + CLI)

[AntoineDao]

Currently the CLI side of queenbee supports a plugin architecture through the use of click-plugins however we do not use such a system for normal modules. ie: auth config classes and functions must all be defined in queenbee and cannot be imported from another plugin module.

This issue is raised in relation to this comment specifically. I agree that this is the preferable way forward but would like to tackle this issue properly at a later date so I can carry on with other dev work.

Some thoughts on plugin architecture reworks:

• Do it like the other ladybug-tools libraries using an importer in the parent package init

"""Honeybee core library."""
import importlib
import pkgutil
from honeybee.logutil import get_logger


logger = get_logger(__name__)

#  find and import honeybee extensions
#  this is a critical step to add additional functionalities to honeybee core library.
extensions = {}
for finder, name, ispkg in pkgutil.iter_modules():
    if not name.startswith('honeybee_') or name.count('_') > 1:
        continue
    try:
        extensions[name] = importlib.import_module(name)
    except Exception:
        logger.exception('Failed to import {0}!'.format(name))
    else:
        logger.info('Successfully imported Honeybee plugin: {}'.format(name))

• Use pop by the creator of saltstack. Here's a good pocast episode about it and here's their docs