Major revision of library internals.

[jheer]

• Breaking: Remove serialized Query functionality; it does not seem to be used at all.
• Breaking: Simplify extensibility to op functions only, remove table method and package registration.
• Breaking: Remove Table.columns() method. Use Table.data() instead.
• Breaking: Remove Table.columnArray() method. Use Table.array() instead.
• Breaking: Rename toArrowBuffer() to toArrowIPC().
• Breaking: Refactor module exports to be flat, including internal classes and toXXX format methods.
• Add lightweight base Table representation, ColumnTable subclass adds transformations and format methods.
• Add array type checks for columns to optimize access.
• Add more Arrow conversions (Date, Decimal, etc.) and corresponding arrowColumn() option flags.
• Add object freeze to table column object.
• Remove internal column wrapper interface, use array-like objects directly.
• Refactor verb definitions to a single location, remove previous engine folder.
• Refactor verb argument parsing to consolidate in top-level verb methods.
• Refactor all Apache Arrow functionality to the arrow folder.
• Improve TypeScript types and testing.
• Update build process, drop node bundle, retain UMD builds.