Add wrapper scripts to pipe training tensors directly to Tensor2Bin

[ftostevin-ont]

This MR adds a wrapper script CreateTrainingTensor that calls CreateTensor{Pileup|FullAlignment} and handles piping the output to Tensor2Bin, in the same way as CallVarBam does with CallVariants. Additionally, UnifyRepresentation similarly calls CreateTensorFullAlignment and handles the piped output directly.
This has the advantage of saving writing and rereading the uncompressed tensors from disk, and allows tensor extraction and compression to run in parallel.

I also add a second script MergeBin that simply merges the individual chunk binaries into one, without changing their contents. This is mainly to limit the number of binary files that need to be passed to training.

One functional change introduced by this is that non-variant site subsampling is done at a variable rate (though targeting a constant variant:non-variant ratio) determined at the level of chunks of sites of size shuffle_bin_size, rather than at a global rate determined over all tensor details files. I have not seen that this significantly affects the resulting output tensors, though in theory the number of non-variant sites included will be sligthly more variable.

This should be backwards-compatible with the previous functionality of Tensor2Bin, though I have not extensively tested this.

[aquaskyline]

#53 and #55 testing in progress.