Task Done Split off the alias and marker layers

split off the alias and marker layers :

+ Done (API is getPaths, uploaded via bulkCreate)

API : aliases : get all alias groups pertaining to a given list of chrs, additional parameter : list of chrs for which aliases have already been received (or some other method to avoid getting the same information again, because large overlap between alias groups of chrs) markers : get the markers of a chr, within a range