Change sample_id with list of cell IDs

[lambdamoses]

Right now the changeSampleIDs function changes a sample_id into another one wherever it occurs, but it can't change cells with the same sample_ids into having different sample_ids such as when splitting samples. Change sample_ids with a list whose names are new sample_ids and values are vectors of cell IDs for each new sample. This is used when using geometry to split samples, say multiple pieces within the same Visium capture area.