Workflow converts input BAM file into bigWig and bedGraph files

Tool to sort and index input BAM/SAM/CRAM. If input `trigger` is set to `true` or isn't set at all (`true` is used by default), run `samtools sort` and `samtools index`, return sorted BAM and BAI/CSI index file. If input `trigger` is set to `false`, return unchanged `sort_input` (BAM/SAM/CRAM) and index (BAI/CSI, if provided in `secondaryFiles`) files, previously staged into output directory.

Before execution `baseCommand`, `sort_input` and `secondaryFiles` (if provided) are staged into directory set as docker parameter `--workdir` (tool's output directory), using `InitialWorkDirRequirement`. Setting `writable: true` makes cwl-runner to make copies of the `sort_input` and `secondaryFiles` (if provided) and mount them to docker container with `rw` mode as part of `--workdir` (if set to false, the files staged into output directory will be mounted to docker container separately with `ro` mode). Because both `samtools sort` and `samtools index` can overwrite files with the same names (and in case of `samtools sort` even the input file can be overwritten), we don't need to rename any of the staged files.

Trigger logic is implemented in two bash scripts set by default as `bash_script_sort` and `bash_script_index` inputs. For both of then, if the first argument $0 (which is `trigger` input) is true, run `samtools sort/index` with the rest of the arguments. If $0 is not true, skip `samtools sort/index` and return `sort_input` and `secondaryFiles` (if provided) staged into output directory.

Input `trigger` is Boolean, but returns String, because of `valueFrom` field. The `valueFrom` is used, because if `trigger` is false, cwl-runner doesn't append this argument at all to the the `baseCommand` - new feature of CWL v1.0.2. Alternatively, `prefix` field could be used, but it causes changing in script logic.

If using `sort_output_filename`, the output file extension should be `*.bam`, because `samtools sort` defines the output file format on the base of the file extension. If `*.sam` is sed as output filename, it cannot be usefully indexed by `samtools index`.

`default_bam` function is used to generate output filename for `samtools sort` if input `sort_output_filename` is not set or when `trigger` is false and we need to return `sort_input` and `secondaryFiles` (if provided) files staged into output directory. Output filename is generated on the base of `sort_input` basename with `.bam` extension by default.

`ext` function is used to return the index file extension (BAI/CSI) based on `csi` and `bai` inputs according to the following logic `csi` && `bai` => BAI !`csi` && !`bai ` => BAI `csi` && !`bai ` => CSI