Fix default exclusion of gitignore directory

[pmai]

Fixes#9

[asadekasam]

OSI CCB 16.10.25: Approved, but merging pending enough memebers to test. Shall be merged offline by 1 of the CCB members

[thomassedlmayer]

pip install . and poetry run pip install . works now again for me on Windows. Also, it works to reference this branch in the pyproject.toml of another project and install it via poetry install as dependency.

poetry install in osi-python itself does still create empty osi3 and osi3trace lib folders but that's not to be solved by this PR.

[TimmRuppert]

The installation using pip from remote (without cloning) works as well.

poetry install in osi-python itself does still create empty osi3 and osi3trace lib folders but that's not to be solved by this PR.

Should this be tracked in a new issue?