Gt4py

**Full Changelog**: https://github.com/GridTools/gt4py/compare/v1.0.2...v1.0.3

First version including the experimental `gt4py.next` aka *Declarative GT4Py*. The `gt4py.next` package is excluded from semantic versioning.

First official release of the Cartesian GT4py.

Last development version using old-style Storage class.

Added
- Remove the `Storage` classes and implement the new _"No Storage"_ concept.
- Support interfaces for calling stencils with arbitrary buffer objects (for details see [docs/arrays.rst](docs/gt4py/arrays.rst) and [PR 868](https://github.com/GridTools/gt4py/pull/868)).
- Updated documentation, logo and license headers.

Changed
- Important `gt4py` package reorganization and modularization.
- Moved most of existing functionality into `gt4py.cartesian`.
- Moved `gtc` package into `gt4py.cartesian`.
- Moved `eve` package into `gt4py`.
- Refactored `gt4py.storage` to avoid dependencies on `gt4py.cartesian`.
- Tests split into sub-packages and reorganized as `unit_tests` and `integration_tests`.