Add code changes for TESTGEN feature

[enriozuni]

Description

This pull request contains required code changes so that the Testgen module that is found here, can be incorporated into CogniCrypt. The module is also called CogniCrypt_TESTGEN and contains the functionality of automatically generating test cases for Java Cryptographic APIs. The work is part of the Master thesis of Rakshit.

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

How Has This Been Tested?

Test Configuration:

• Eclipse Version: 2020-06
• Java Version: 1.8
• OS: Windows 10

Checklist:

• [ ] I have performed a self-review of my own code
• [ ] I have commented on my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [X] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes