Rename all D-Bus properties to conform to D-Bus naming conventions;
all programs changed.

Also rename client setting "approved_delay" to "approval_delay", and
"approved_duration" to "approval_duration"; all programs changed.

* mandos (ClientDBus.NeedApproval): Bug fix: send an UInt64, not a
                                    float.
  (ClientDBus.ApprovedByDefault_dbus_property,
  ClientDBus.ApprovalDelay_dbus_property,
  ClientDBus.ApprovalDuration_dbus_property): Bug fix: send
                                              PropertyChanged signal.