Made watchable_t and the like use std::function.
Removed boost/function.hpp from watchable.hpp.
Made json_adapter.hpp not include boost/function.hpp.
Removed boost/function.hpp from semilattice/view.hpp.
Removed boost/function.hpp from death_runner.hpp.
Removed boost/function from network.hpp.
Removed bosot/functionh.pp from clustering_utils.hpp.
Removed boost/function.hpp from arch/io/disk headers.
Removed boost/function.hpp from multistore.hpp.
Removed some last boost/function includes.