Implement twisted diagram monoids

[flsmith]

It would be good to natively support finite twisted diagrams, i.e. ones where multiplication of elements accounts for any floating loops.

[james-d-mitchell]

Are the elements pairs consisting of a bipartition and a non-negative integer, with multiplication given by multiplying the bipartitions and adding the number of floating components to something?

[flsmith]

This is my understanding, with the proviso that in order to get finite semigroups you need to truncate at some point (which I think means multiplying to some 0 once the number of components gets too large).