Make eodal_viewer a proper package

[lukasValentin]

Make eodal_viewer a proper package so that it can be installed using git.

• [x] rename package to a more appropriate name (it downloads TIF-files)
• [x] add setup.py
• [x] make inputs of main.py CLI arguments
• [x] add GPL license to module doc strings
• [x] update README.md
• [x] add a proper CLI for the package
• [x] proper testing for Sentinel-2 and Landsat
• [x] add Github workflow for CI/CD pipeline (testing and code coverage)

[lukasValentin]

New name eodal_basetiffs

[lukasValentin]

to do: change the name in all source code files and rename the source code folder

[lukasValentin]

related PRs #6 and #7