Updates to allow more robust naming and usage of plugins

[asgibson]

Plugins can now be named something other than the module name
This also allows re-use of the same plugin module in a single config file

• each plugin will be a different instance

The __init__.py file is required to exist in the directory for the plugin module
Backward compatibility with including __init__.py at end of module path is included

• config path must at least point to directory of module that will be used
• having the __init__.py in the plugin path is now optional

Module is now dynamically known by last dir in path (minus init file if included)
Unit tests updated to reflect changes

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (c2e1d42) 100.00% compared to head (16d382b) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #119 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 25 25 Lines 942 951 +9 Branches 131 133 +2 ========================================= + Hits 942 951 +9 ```

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