Write specific advanced Nextflow examples

[MehmedGIT]

1. Write an example Nextflow script that uses processes with an exec block that does REST API calls to the outside world. Then parses the received responses.
2. Write an example Nextflow script with branching support, i.e., dynamic workflows. The branching could happen based on the output results of the previous processors or based on the received responses from REST API calls.

A combination of the above examples could also be provided in a single Nextflow script.

3. Write an example Nextflow script that will use page-id to do page-wise processing in parallel. Since OCR-D processors do not provide page-wise processing yet, the script implementation will use simple images with assigned numbers.

[MehmedGIT]

The two Nextflow scripts were added here. Read the readme of section workflow7 and check inside folder workflow7.