Beta release of v3.0.0-beta.14

Breaking changes:

• Rename tuples expression function to data.
• Update View state method to include modified data and recurse into sub-contexts.

Other changes:

• Add dependency tracking for point/interval selection expression functions.
• Safeguard file system loading in vega-loader.
• Limit View preventDefault to events originating from the view.
• Fix View preventDefault getter/setter bug.