ctools 8.x-3.0-alpha24

Changes since 8.x-3.0-alpha23:

• A few minor fixes to the tests to get coverage passing. Still at least one error in all of this.
• Added a context schema to match the new context classes, updated the ContextConfigure class for the required "exists" property of machine_name elements, and added the new context_mapper service definition.
• Reworked the context classes to actually manage contexts instead of TypedDataResolver based token representations of contexts.
• Merge branch '8.x-3.x' of git.drupal.org:project/ctools into 8.x-3.x
• moving the ContextMapper and EntityLazyLoadContext classes into ctools as always intended.
• Copying the existing ManageContext and ContextConfigure classes into a name that shows these existing classes are related to the TypedDataResolver and not normal contexts and relationship.
• adding a language relationship and some initial test coverage.
• Updated the entity relationship so that the default on the context definition matches the context value
• abstracted the creation of derivative labels and added test coverage to ensure they are correct.
• reworked the data type determination to focus on primitives for the non-entity plugin
• initial commit of entity relationship plugin and refactored tests and deriver to be more universally usable
• removing an unnecessary variable in the TypedDataRelationshipPluginTest.
• abstracted the basic logic of the TypedDataRelationshipDeriver into an abstract class other derivers can leverage.
• added a new Relationship plugin type with an initial implementation that can retrieve raw values from typed data relationships on complex data objects like entities. Also moved the TypedDataResolverTest to the appropriate directory structure to actually get run.