Dagster

- Adds a `type_check` parameter to `PythonObjectType`, `as_dagster_type`, and `as_dagster_type` to
enable custom type checks in place of default `isinstance` checks.
See documentation here:
https://dagster.readthedocs.io/en/latest/sections/learn/tutorial/types.html#custom-type-checks
- Improved the type inference experience by automatically wrapping bare python types as dagster
types.
- Reworked our tutorial (now with more compelling/scary breakfast cereal examples) and public API
documentation.
See the new tutorial here:
https://dagster.readthedocs.io/en/latest/sections/learn/tutorial/index.html
- New solids explorer in Dagit allows you to browse and search for solids used across the
repository.

- Enabled solid dependency selection in the Dagit search filter.

- To select a solid and its upstream dependencies, search `+{solid_name}`.
- To select a solid and its downstream dependents, search `{solid_name}+`.
- For both search `+{solid_name}+`.

- Added a terminate button in Dagit to terminate an active run.

- Added an `--output` flag to `dagster-graphql` CLI.
- Added confirmation step for `dagster run wipe` and `dagster schedule wipe` commands (Thanks
shahvineet98).
- Fixed a wrong title in the `dagster-snowflake` library README (Thanks Step2Web).

- Changed composition functions `pipeline` and `composite_solid` to automatically give solids
aliases with an incrementing integer suffix when there are conflicts. This removes to the need
to manually alias solid definitions that are used multiple times.
- Add `dagster schedule wipe` command to delete all schedules and remove all schedule cron jobs
- `execute_solid` test util now works on composite solids.
- Docs and example improvements: https://dagster.readthedocs.io/
- Added `--remote` flag to `dagster-graphql` for querying remote Dagit servers.
- Fixed issue with duplicate run tag autocomplete suggestions in Dagit (1839)
- Fixed Windows 10 / py3.6+ bug causing pipeline execution failures

- Fixed an issue where Dagster public images tagged `latest` on Docker Hub were erroneously
published with an older version of Dagster (1814)
- Fixed an issue where the most recent scheduled run was not displayed in Dagit (1815)
- Fixed a bug with the `dagster schedule start --start-all` command (1812)
- Added a new scheduler command to restart a schedule: `dagster schedule restart`. Also added a
flag to restart all running schedules: `dagster schedule restart --restart-all-running`.

**New**

This major release includes features for scheduling, operating, and executing pipelines
that elevate Dagit and dagster from a local development tool to a deployable service.

- `DagsterInstance` introduced as centralized system to control run, event, compute log,
and local intermediates storage.
- A `Scheduler` abstraction has been introduced along side an initial implementation of
`SystemCronScheduler` in `dagster-cron`.
- `dagster-aws` has been extended with a CLI for deploying dagster to AWS. This can spin
up a Dagit node and all the supporting infrastructure—security group, RDS PostgreSQL
instance, etc.—without having to touch the AWS console, and for deploying your code
to that instance.
- **Dagit**
- `Runs`: a completely overhauled Runs history page. Includes the ability to `Retry`,
`Cancel`, and `Delete` pipeline runs from the new runs page.
- `Scheduler`: a page for viewing and interacting with schedules.
- `Compute Logs`: stdout and stderr are now viewable on a per execution step basis in each run.
This is available in real time for currently executing runs and for historical runs.
- A `Reload` button in the top right in Dagit restarts the web-server process and updates
the UI to reflect repo changes, including DAG structure, solid names, type names, etc.
This replaces the previous file system watching behavior.

**Breaking Changes**

- `--log` and `--log-dir` no longer supported as CLI args. Existing runs and events stored
via these flags are no longer compatible with current storage.
- `raise_on_error` moved from in process executor config to argument to arguments in
python API methods such as `execute_pipeline`

- Fixes an issue using custom types for fan-in dependencies with intermediate storage.

- Fixes an issue running some Dagstermill notebooks on Windows.
- Fixes a transitive dependency issue with Airflow.
- Bugfixes, performance improvements, and better documentation.