Paralogues taxonomy level

Good morning,

The commits mainly add a description for the "taxonomy level" of the paralogues, by using a tooltip (I'm reusing the code for glossary terms). I've also slightly reworked other files so that the node in the species-tree is used instead of its name ("taxonomy_level" or "homology_subtype") 

It's working on my sandbox for both [ancient](http://enssand-01.internal.sanger.ac.uk:9073/Homo_sapiens/Gene/Compara_Paralog?g=ENSG00000163823;r=3:46201709-46208396;t=ENST00000296140) and [species-specific](
http://enssand-01.internal.sanger.ac.uk:9073/Ornithorhynchus_anatinus/Gene/Compara_Paralog?db=core;g=ENSOANG00000015481;r=Ultra336:825655-866744) paralogues:


Matthieu
PS: The commits have to be merged in master as well