Setigen

Rename default branch to `main`, edit README image links.

Update README.md image calls with absolute hyperlink paths.

Support creation of synthetic raw voltage data.

Create synthetic real voltages, pass through a software-based signal processing pipeline, including a polyphase filterbank, and save to GUPPI RAW format. Supports adding Gaussian real voltage noise, drifting chirp signals, and custom noise functions. Implements quantization before and after filterbank channelization.

Copy array instead of passing a reference when instantiating Frame using existing data

Change filename within a Frame's Waterfall.container to work better with blimpy, and support changing max_load parameter on save_fil and save_hdf5. Allows larger arrays to be created and saved to file via blimpy.

Update requirements.