Randomize seed on batch generation

[barepixels]

Am reposting this from lllyasviel#306

The seed does not randomize between images when batch generating images, it increments by 1.

Is this by design or a bug, now it only randomizes if I generate 1 image at a time?

I can see the value with incrementing but it would be very nice to have the option to randomize between images too.

I just verified with batch, it increments by 1
@MoonRide303 Maybe we can have an "increment" next to the "random" option for Single and Batch

[MoonRide303]

@barepixels I've explained it in the original issue - it's only necessary for first number to be random (to avoid using popular numbers), and following seeds can be simply increased by 1. They don't need to be far away to generate completely different image.