Static-frame

Introduced the ``Batch``, a lazy, parallel processor of groups of ``Frame``.

``Index`` and ``IndexHierarchy`` ``intersection()`` and ``union()`` now accept ``*args``, performing the set operation iteratively on all arguments.

Revised default aggregation function to ``Frame.pivot``.

Fixed issue in writing SQLite stores from ``Frame`` labelled with strings containing hyphens.

Added `include_index_name`, `include_columns_name` to ``Frame.to_delimited``.

Added `include_index_name`, `include_columns_name` to ``StoreConfig`` and ``Frame.to_xlsx`` interfaces.

Added `index_name_depth_level` and `columns_name_depth_level` to `Frame.from_delimited` and related methods.

Added `index_name_depth_level`, `columns_name_depth_level` to ``StoreConfig`` and ``Frame.from_xlsx`` interfaces.

Improved implementation of ``Frame.pivot``.

Removed class-level documentation injection, permitting better static analysis.

Corrected issue in appending tuples to an empty ``IndexGO``.

Added ``Frame.from_clipboard()`` and ``Frame.to_clipboard()``.

Added ``Frame.pivot_stack()`` and ``Frame.pivot_unstack()``.

Fixed flaw in difference operations on ``IndexDatetime`` subclasses of equivalent indices.

Frame.from_parquet`` and ``Frame.from_arrow`` now accept a ``dtypes`` argument.

All ``PathLike`` path objects now accepted wherever ``Path`` objects were previously.

Added ``fillna`` methods to ``Index``, ``IndexHierarchy``.

Added to ``StoreFilter`` the following parameters: ``value_format_float_positional``, ``value_format_float_scientific``, ``value_format_complex_positional``, ``value_format_complex_scientific``.

``Index`` and ``IndexHierarchy`` will reuse instances for set operations on equivalent indices.

Added ``IndexHierarchy.from_names`` constructor for creating zero-length ``IndexHierarchy``.

Refinements to ``IndexHierarchy`` to support grow-only mutation from zero length.