Write metadata to a txt file

[vladoatanasov]

I find it useful to write the metadata from the gradio UI to a text file in the output dir, as I tend to forget what parameters I've used for a prompt.

A sample output:

fractal forest, intricate detail
--------------
ddim_steps: 50
n_iter: 1
batch_size: 1
Height: 512
Width: 512
scale: 7.5
ddim_eta: 0
unet_bs: 1
device: cuda
seed: 907564
turbo: False
full_precision: True
sampler: plms
--------------
Output: 
Samples finished in 2.292 minutes and exported to outputs/txt2img-samples\fractal_forest,_intricate_detail
Seeds used = 907563

[vladoatanasov]

Seeing #123 now. This is a much better approach