transpose functions for Matrix

[m-tosch]

transpose() which transposes the matrix object itself transposed() which returns a new, transposed matrix object would be consistent with other existing function names... but... transposing the object itself would probably require some kind of bool variable inside the class that indicates if transpose() has been called on the matrix, since switching dimensions N and M for the statically allocated Matrix object is not possible. An option would be to break consistency, and make transpose() return a new, transposed Matrix object.

• add convenience functions ✔
• add explicit inst. ✔
• add tests ✔

[m-tosch]

indeed implemented a transpose() funtion that creates and returns a new, transposed matrix object