* Fixed Options for extra_params in UI
* Enhanced meta-programming for models
* Plugins can be imported from a python file if they're named
`senpy_<whatever>.py>` (no need for `.senpy` anymore!)
* Add docstings and tests to most plugins
* Read plugin description from the docstring
* Refactor code to get rid of unnecessary `.senpy`s
* Load models, plugins and utils into the main namespace (see __init__.py)
* Enhanced plugin development/experience with utils (easy_test, easy_serve)
* Fix bug in check_template that wouldn't check objects
* Make model defaults a private variable
* Add option to list loaded plugins in CLI
* Update docs
We've changed the way plugins are activated, and removed the notion of
deactivated plugins.
Now plugins activate asynchronously.
When calling a plugin, it will be activated if it wasn't, and the call will wait
for the plugin to be fully activated.
