First unit tests

First examples of unit tests for qim3d

We have lots of warnings, but we can ignore them for the moment.

To run tests, navigate to the project directory and run:

pytest -v --disable-warnings

This is the expected result for this merge:

=============================================== test session starts ================================================
platform linux -- Python 3.10.11, pytest-7.3.2, pluggy-1.0.0 -- /home/fima/miniconda3/envs/dev/bin/python
cachedir: .pytest_cache
rootdir: /home/fima/qim
plugins: anyio-3.6.2
collected 5 items                                                                                                  

qim3d/tests/gui/test_local_thickness.py::test_starting_class PASSED                                          [ 20%]
qim3d/tests/gui/test_local_thickness.py::test_app_launch PASSED                                              [ 40%]
qim3d/tests/utils/test_internal_tools.py::test_mock_plot PASSED                                              [ 60%]
qim3d/tests/utils/test_internal_tools.py::test_mock_write_file PASSED                                        [ 80%]
qim3d/tests/utils/test_internal_tools.py::test_get_local_ip PASSED                                           [100%]

========================================= 5 passed, 142 warnings in 4.42s ==========================================