Draft: Add PTWrapper support

• Allow the users to install the PTWrapper as an extra dependency:

python -m pip install esa-ptr[ptwrapper]
# or
poetry install --extras ptwrapper

• Add extra install documentation (+ README)

• Retrieve PTWrapper libraries versions:

>>> from ptr.ptwrapper import get_versions
>>> get_versions()
{'OSVE': '1.6.0', 'Interface': '1.6.0', 'AGM': '9.3.0.p1', 'EPS': '9.3.0'}

• Add PTWrapper get_attitude() query to by-pass PT API call in agm_simulation().