[BUG] StudentT: Distribution name is incorrectly overwritten when subclassing

[AKuederle]

Describe the bug
As the name of the distribution is set in the __init__, any distribution that subclasses another distribution, needs to make sure that name is set after calling super.

This goes wrong for the StudentT distribution.

StudentT().name # <- prints "Normal"

This is an easy fix in this case, but it might be worse it to change the way name is set.
As it is a class and not an instance variable, it might be easier to just define it in the class body directly and not the __init__. This way it can be overwritten without worrying about the correct order in the init.