Add a function for chia plots check to get rid of low quality plot

[Hoktek]

I like the new function of bladebit_cuda 3.1 --check-threshold that can get rid of the low quality plots before put in the farm.

It would be great if chia plots check have a function that can scan and get rid of low quality plots in the farm.

[hajes]

@Hoktek what is low quality plot?