Caustic

Updates to a number of features including:
- multiplane
- object names
- reformat `source` to now be more general `light`
- forward raytrace
- new basic simulator object

Bug fixes to TNFW class. Pixelated Convergence also has more correct FFT convolution.

Bug fix for pixelated convergence FFT padding mode. Caustic now has a website! TNFW online mostly

Added the TNFW lens to caustic

Multiplane lensing now includes Effective convergence including both the divergence and curl components.

Forward raytracing now available.

mass sheet lens added

bug fixes in graph viewer and pixelscale arguments

Mechanics upgrade. The parameter handling system has been upgraded internally. It now allows batching and better control over dtype. The Packed management system now better understands inputs to functions, it can handle keywords in arguments. The name for every module is now optional, it will automatically generate a name if none is given. Many more small changes.