added flatten_tree method, fixed get_all_leaves method, cleaned up the child/parent link/unlink code
added flatten_tree method, fixed get_all_leaves method, cleaned up the
child/parent link/unlink code

danstaines/ensembl-compara,kumarsaurabh20/ensembl-compara,Ensembl/ensembl-compara,Ensembl/ensembl-compara,kumarsaurabh20/ensembl-compara,ckongEbi/ensembl-compara,Ensembl/ensembl-compara,danstaines/ensembl-compara,etapanari/ensembl-compara,Ensembl/ensembl-compara,dbolser-ebi/ensembl-compara,ckongEbi/ensembl-compara,kumarsaurabh20/ensembl-compara,kumarsaurabh20/ensembl-compara,etapanari/ensembl-compara,Ensembl/ensembl-compara,danstaines/ensembl-compara,Ensembl/ensembl-compara,danstaines/ensembl-compara,ckongEbi/ensembl-compara,Ensembl/ensembl-compara,dbolser-ebi/ensembl-compara,danstaines/ensembl-compara,etapanari/ensembl-compara,Ensembl/ensembl-compara,dbolser-ebi/ensembl-compara,etapanari/ensembl-compara