Previously the configuration values were separated out to
gradle.properties, for no real benefit. This puts the configuration all
in one place.

* Fix file permissions.

* Delete dead test.
Update postcommit project paths.
Drop 'Gradle' from Python precommit PR trigger.

Revert components that we are not ready to merge yet. These will continue to be developed in another branch.

Cleanup types in Beam Schema. Add a metadata field to TypeDescriptor, so that Calcite can distinguish multiple types that all map to the same Beam schema type.

Refactor Schema: Schema now is a fully-specified based on primitive types. Nested Schemas and arrays are also supported.

Add SchemaRegistry to Pipeline object.