switched all getter/setter methods to use shift methodology to avoid any problems related to setting undef or '0' values.
switched all getter/setter methods to use shift methodology to avoid
any problems related to setting undef or '0' values.

Ensembl/ensembl-hive,Ensembl/ensembl-hive,Ensembl/ensembl-hive,Ensembl/ensembl-hive