Add more settings / functionnality

[Yakonche]

• A possibility to generate both a "positive" prompt AND a negative prompt (calculate one then the other in the same load, so that after clicking on "Generate", we obtain both) at the same time.

• The possibility of selecting several models which will display their results in the WebUI as a list, and why not also to download as a file (txt, csv, etc...).

• Possibly, a description of the characteristics of the different CLIP models (like the weight and other thing).

These features would save a lot of time and comfort.

[alienhd]

• The possibility to change the actual Blip model would also be a very useful feature.

[miasik]

Option to select several models, process them one by one for an entire batch, save their merged output as a single result per image.

[miasik]

Option to add content to a .txt if it already exists instead of overwriting.