feat: add support for multi-lane samples

In the previous version, the workflow was working under the assumption that each sample name only appears once in the samples table. This was a bottleneck for incorporating multi-lane samples, as this led to multiple lines with the same sample (each line one lane with individual paths to fastq files). This is now dealt in the following way: same mate files with the same sample name are concatenated in the beginning and a function ensures that features that should be sample-dependent are not returned multiple times (due to the multiple-lines with same sample issue). Additionally, a separate test is created to test this functionality, with a samples table containing multi-lane samples.

Closes #115 (closed)