attempting to resolve Issue #4

More details are in the comments to Issue #4
Forgot about the case when we are not logging but looking for something and found it.
Adding initialisation of schreier trees in the case that an orbit has seeds
fixed bug in last

Tried to add values fail for seeds to schreiergen/pos when we didn’t
have a schreier tree.
Merge pull request #5 from james-d-mitchell/master

Resolved Issue #4 and a further bug caused by orbits with seeds