Explainerdashboard

New Features
- `ExplainerHub` now does user managment through `Flask-Login` and a `user.json` file
- Can now set specific access policies for specific explainer with `db_users` parameter
- adds an `explainerhub` cli to start explainerhubs and do user management from the command-line

Bug fixes:
- fixes 52

New Features
- Introducing `ExplainerHub`: combine multiple dashboards together behind a single frontend with convenient url paths.
- code example:
python
db1 = ExplainerDashboard(explainer, title="Dashboard One", name='db1')
db2 = ExplainerDashboard(explainer2, title="Dashboard Two", name='project_alpha', description="New proposed model")

hub = ExplainerHub([db1, db2])
hub.run()

store an recover from config:
hub.to_yaml("hub.yaml")
hub2 = ExplainerHub.from_config("hub.yaml")

- adds option `dump_explainer` to `ExplainerDashboard.to_yaml()` to automatically
dump the `explainer` along with the `.yaml`.
- adds option `use_waitress` to `ExplainerDashboard.run()` and `ExplainerHub.run()`, to use the `waitress` python webserver instead of the `Flask` development server
- adds parameters to `ExplainerDashboard`:
- `name`: this will be used to assign a url for `ExplainerHub` (otherwise defaults to `dashboard1`, `dashboard2`, etc
- `description`: this will be used for the title tooltip in the dashboard
and in the `ExplainerHub` frontend.


Improvements
- the `cli` now uses the `waitress` server by default.

Bug fix/Improvement
- Makes component `name` property for the default composites deterministic instead
of random uuid, now also working when loading a dashboard `.from_config()`
- note however that for custom `ExplainerComponents` the user is still responsible
for making sure that all subcomponents get assigned a deterministic
`name` (otherwise random uuid names get assigned at dashboard start,
which might differ across nodes in e.g. docker swarm deployments)
- Calling `self.register_components()` no longer necessary.

Bug fix/Improvement
- Makes component `name` property for the default composites deterministic instead of random uuid.
This should help remedy bugs with deployment using e.g. docker swarm.
- When you pass a list of `ExplainerComponents` to ExplainerDashboard the tabs will get names `'1'`, `'2'`, `'3'`, etc.
- If you then make sure that subcomponents get passed a name like `name=self.name+"1"`, then subcomponents will have deterministic names as well.
- this has been implemented for the default `Composites` that make up the default `explainerdashboard`