MDS-353: use get_namespaces_states

The whole info for namespace is getting from mastermind by get_namespaces_states.

Following mastermind handlers are no longer used:
get_group_weights, get_namespaces_settings, get_couples_list, get_namespaces_statistics

Added dependency on libkora-util

'elliptics-remotes' cache and 'cache-groups' cache will not applied if they are empty,

Libmastermind uses raw mastermind responses for caches' serialization,

Expired cache is no longer removed, it just is not used.