Swiftgalaxy

Adds support for using swiftgalaxy without a halo catalogue, e.g. to select particles within some spatial region and/or boolean mask and then make use of the rest of the swiftgalaxy features (spherical/cylindrical coordinates, masking, consistent coordinate frame, etc.). Also adds a cookbook example to the documentation for selecting all particles within a spherical aperture, with or without a halo catalogue.

Completes support for caesar halo catalogues now that caesar outputs the spatial extent of groups in the catalogue (so that we can use this to define a spatial mask for swiftsimio). Older caesar outputs are still compatible, but will inefficiently read the entire simulation volume (a warning will be issued at runtime in this case).

Added support for Caesar halo catalogues.

Abandon setup.py based build system in favour of pyproject based build system.

Support for changes in velociraptor-python package (v0.16.1).

The initial release of SWIFTGalaxy, including:
- Automated loading of particles corresponding to a galaxy identified by a halo finder.
- Support for the Velociraptor halo finder.
- Exposure of the integrated properties calculated by the halo finder.
- Automatic recentering in the galaxy frame, and coordinate transformations (rotation, translation, boost).
- Additional coordinates (cylindrical & spherical) on-demand.
- Masking to select subsets of particles.