Add a simple working pycomlink example notebook

[cchwala]

Adding a very basic notebook to show that pycomlink works in the sandbox. This example shall be extended later with one of the new open OS datasets.

TODO:

• [x] adjust info in readme with correct git clone with submodules
• [x] run pycomlink example notebook directly from sandbox binder (works, but needs adjustment see comment below)
• [x] add very basic pycomlink example notebook as basis for processing other datasets

[github-actions[bot]]

:point_left: Launch a binder notebook on branch _cchwala/OPENSENSE_sandbox/add_pycomlinkprocessing

[cchwala]

Note that the pycomlink example notebooks do not yet run because pycomlink is not installed. It is added to the repo as submodule. Hence, it has to be added in an example notebook from the pycomlink repo with

import sys
sys.path.append('../')

I checked, and the "Basic CML processing worflow" notebook runs without problems.

I want to add a new an almost empty notebook to the root dir of the sandbox repo, which can be the basis for processing another open dataset.

[cchwala]

Note that I had a half-baked pycomlink example notebook with Dutch CML data here. I removed it in the last commit to merge something clean here.

[cchwala]

When trying a git clone --recursive in a new tmp dir if found that the pycomlink submodule is in a detached state. Checking in my local repo where I do the dev work for the sandbox, I found the same

$ git status
HEAD detached at 12fc302
nothing to commit, working tree clean

I am not familiar enough with git submodules to understand myself what went wrong, but this SO answer seems to explain and provide a solution.

⚠️ Since we have several submodules in this repo we should really understand what is going on with git submodules ⚠️

[cchwala]

... 🤔 maybe we do not have to care much about the detached head of the submodule since, for us, it is just important that the correct commit is included. Only if we want to commit changes back upstream to the submodule repo we need to track a branch.