Add ability to request listing and deleting only for dynamic states.

This can be useful, when net.inet.ip.fw.dyn_keep_states is enabled, but
after rules reloading some state must be deleted. Added new flag '-D'
for such purpose.

Retire '-e' flag, since there can not be expired states in the meaning
that this flag historically had.

Also add "verbose" mode for listing of dynamic states, it can be enabled
with '-v' flag and adds additional information to states list. This can
be useful for debugging.

Obtained from: Yandex LLC
MFC after: 2 months
Sponsored by: Yandex LLC