Stave

Update the configuration structure
1. Remove `settings.py` and `wsgi.py` from `stave` package.
Allow users to provide their own customized django settings.
2. Refactor the configuration logic.
Add a `StaveConfig` class to manage the access/update of configuration.
3. Add a user-friendly interactive interface in CLI to guide users through the initial configuration process.

For more details, refer to 207.

* Add detailed instructions to `README.md`
* How to switch port number
* How to configure database path, allowed host names, etc.
* How to import/export project of stave
* Fix nlp.py
* Update `Datapack` serialization interface
* Some version bumps for frontend packages

This initial release contains the basic visualization components, a minimal user management system for team annotation, and a prototyped plug-in system, the details include:

1. Basic Span Link visualizer for forte data packs.
a. Spans visualized as highlighted and bracketed text.
b. Links visualized as lines between spans.
c. Scope selector to allow the viewer to focus on one particular annotation type.
d. Legend to show the color of each span.
e. The annotation information box to show the information of the annotation.
1. Basic data edit functions.
a. Span annotation as highlighting a span, or clicking the begin and end of the text.
b. Link annotation by drag and drop using the small + sign on the span corner.
c. Group annotation by adding elements into the Group plugin
1. Two example plugins: Group viewer and DialogueBox.
1. A database structure that manages documents as project, and user permission on the project level.
1. A sample Job system that tracks whether a document is finished.
1. A configuration system that can change what interfaces are used.
1. Project and User panel for the basic project and user management.

This release includes updates in naming, workflow, and nlp model handling.
- naming
- Update the package name from `nlpviewer_backend` to `stave_backend`.
- Update CLI subcommand `stave load` to `stave load-samples`
- Update the CLI flag `--load` to `--load-samples`.
- workflow
- Replace Travis CI test with GitHub workflow.
- nlp model
- Use `RemoteProcessor` to load NLP pipeline from remote service instead of directly importing specific processors from `forte`.
- Add a new optional field `remoteConfigs` in default project configuration for users to configure remote service.

We release the first pre-built Stave!

1. This release allows Stave to be installed via `pip install stave`.
1. The viewer mode: now you can view the NLP visualization. No need to log in to the full interface anymore!
1. Bugfix on UUID issue.
1. Bugfix on short id issue.