Fix txt2img save bugs, enable upload of training images, allow google drive download of models

[jrobsontull]

• Limit length of txt2img outputs to preventing crash upon image saving with file names that are too long.
• Attach unique ID to txt2img outputs to prevent overwriting old outputs where prompt is the same.
• Enable downloading of models from Google Drive.
• Facilitate direct upload of training images.

[chelfyn]

I do this by hand, just create the directory and drop ion .pngs. works fine