List base systems.
Example:
< GET /admin/base-systems > 200 Ok > > [ > { > basesystem: "SLES10_SP4" > , enabled: false > } > , { > basesystem: "SLED11_SP1" > , enabled: true > } > , { > basesystem: "SLES11_SP1" > , enabled: true > } > , { > basesystem: "12.2" > , enabled: true > } > # ... > ]