Remove NameIsomorphismClass

[fingolfin]

Remove the undocumented attribute "NameIsomorphismClass". It was added
2000-01-05 by Hans Ulrich Besche, and always was marked as experimental.
Furthermore, it was only available as a pre-computed value for pc groups
constructed via CyclicGroup, and some groups constructed via SmallGroup.

As a replacement, you can use StructureDescription.

The only user visible change is that the output of SmallGroupsInformation
for products of three distinct primes does not list the isomorphism classes
anymore. But since other SmallGroupsInformation methods also don't do
that, this seems like an acceptable loss.

[olexandr-konovalov]

@fingolfin thanks. So, as the consequence, instead of e.g.

gap> SmallGroupsInformation(2*5*19);

  There are 4 groups of order 190.
    1 is of type D10x19.
    2 is of type D38x5.
    3 - 3 are of types 5:2+19:2.
    4 is of type c190.

  The groups whose order factorises in at most 3 primes 
  have been classified by O. Hoelder. This classification is 
  used in the SmallGroups library. 

  This size belongs to layer 1 of the SmallGroups library. 
  IdSmallGroup is available for this size. 

we will have just

gap> SmallGroupsInformation(2*5*19);

  There are 4 groups of order 190.

  The groups whose order factorises in at most 3 primes 
  have been classified by O. Hoelder. This classification is 
  used in the SmallGroups library. 

  This size belongs to layer 1 of the SmallGroups library. 
  IdSmallGroup is available for this size. 

My first reaction was that I don't want to lose this functionality, but then I started to think that its format is not unified with StructureDescription; bringing it to the same form may require an extra work; OTOH, StructureDescription works just fine for these groups, and their number does not constitute a computational challenge. So I agree with @fingolfin that this is an "acceptable loss".