SampleD with a non-spherical Gaussian convolution matrix (with standard base and center 0)

[Marvin-Beckmann]

Description

This PR implements...

• SampleD with a non-spherical Gaussian convolution matrix (with standard base and center 0)

I decided to only implement the common version for now, as the more general version requires more extensive testing and as of right now, I only need the common version.

The PR is based on Algorithm 1 from https://link.springer.com/chapter/10.1007/978-3-642-14623-7_5.

Testing

• I added basic working examples (possibly in doc-comment)
• I triggered all possible errors in my test in every possible way
• I included tests for all reasonable edge cases

Checklist:

• I have performed a self-review of my own code
  • The code provides good readability and maintainability s.t. it fulfills best practices like talking code, modularity, ...
    • The chosen implementation is not more complex than it has to be
  • My code should work as intended and no side effects occur (e.g. memory leaks)
  • The doc comments fit our style guide
  • I have credited related sources if needed