Implement configuration for handling artifact ratings from a file

[sourabhsparkala]

Fixes #743 (duplicate)
Fixes #553

[SebastianWolf-SAP]

I have to admit that I probably don't know enough of the whole codebase to really assess these considerably big changes properly. In addition, I don't have enough time in the next days to dig deeper here. 😞
Therefore, just a few remarks from my side that come to my mind:

• The additional (command-line) configuration option(s) should probably be documented on GitHub Pages, i.e. on https://sap.github.io/fosstars-rating-core/getting_oss_security_rating.html or https://sap.github.io/fosstars-rating-core/getting_oss_rules_of_play_rating.html
• Compared to the number of changes in the respective files and the additional option for configuration, the number of tests that have been changed or added seem to be rather small.

[sourabhsparkala]

I have to admit that I probably don't know enough of the whole codebase to really assess these considerably big changes properly. In addition, I don't have enough time in the next days to dig deeper here. 😞 Therefore, just a few remarks from my side that come to my mind:

• The additional (command-line) configuration option(s) should probably be documented on GitHub Pages, i.e. on https://sap.github.io/fosstars-rating-core/getting_oss_security_rating.html or https://sap.github.io/fosstars-rating-core/getting_oss_rules_of_play_rating.html
• Compared to the number of changes in the respective files and the additional option for configuration, the number of tests that have been changed or added seem to be rather small.

You are right. I will find some time to update the document. Also, I will work on the test cases :)