Breaking changes: db_id type, cancelled state, deserialization and documentation

[gpetretto]

Some changes that may impact the usage of jobflow-remote.

Breaking changes:

• the db_id is now a str and not an int anymore. It was suggested to ease the merge of different databases
• to include the additional options in the queue section of the project document the Project model has changed. An additional indentation layer should be added to a previous configuration file for the queue section. Here is an example of the new version:

  queue:
    store:
      type: MongoStore
      host: localhost
      database: db_name
      username: bob
      password: secret_password
      collection_name: jobs

• The job state CANCELLED has been changed to USER_STOPPED to reduce the usage of different words that could create confusion.

A change that does not break the backward compatibility but could be a source of bugs is the removal of the deserialization of objects in the Runner. Following issue #41. A machine only running the daemon still cannot avoid the presence of flows packages. materialsproject/jobflow#512 needs to be merged before enabling it.

In addition a few bugfix and more documentation.