Implement method of decomposing multigene trees into multiple single-copy gene trees

[ChrisCreevey]

This would allow the user to get the most out of the data they have.
Pro: Allows decomposition of multi-copy gene families into their orthologous sub-families.
Con: Could easily result in paralogous gene families, especially where alternative cpoies have been lost in species - but perhaps no more than may be already happening in "single-copy" gene famililes?