add CI test with full realistic workflow on sample data about ocrd_all

[M3ssman]

As this is designed as an OCR-D-Container-Systemtest, the workflow should focus on module integration, especially with known incompatibilities and, as to provide some sort of regression testing, on previously solved problems.

[stweil]

Some questions:

• When should such a CI test be triggered? Only for releases?
• Should it use a Docker container or use a separate build?
• On which platform should it run? Circle CI? Travis CI? GitHub Actions?

[bertsky]

* When should such a CI test be triggered? Only for releases?

As outlined above: for every new commit on a PR branch (via CircleCI rule build).

* Should it use a Docker container or use a separate build?

Good question. I have a feeling they are almost always the same, but you never know. So let's do the "harder" test, running all the above within a docker run ocrd/all:maximum (with appropriate mount points etc).

* On which platform should it run? Circle CI? Travis CI? GitHub Actions?

I am still with CircleCI, as everything has been set up already, and one could easily add more platforms there in the future.

[stweil]

I am still with CircleCI

Personally I don't have access to the CircleCI results. I started several times to look for an account and always decided against it because I did not like to give them the required rights.

[bertsky]

As this is designed as an OCR-D-Container-Systemtest, the workflow should focus on module integration, especially with known incompatibilities and, as to provide some sort of regression testing, on previously solved problems.

We probably could do more in this regard, but #362 contains a first-order approximation (make test-workflow).