Implement the vir*IsActive vir*IsPersistent methods for virDomainPtr
virNetworkPtr, virStoragePoolPtr and virInterfacePtr. Implement the
virConnectIsSecure & virConnectIsEncrypted fir virConnectPtr

* Virt.xs: Implement C binding to new methods
* lib/Sys/Virt.pm, lib/Sys/Virt/Domain.pm, lib/Sys/Virt/Interface.pm,
  lib/Sys/Virt/Network.pm, lib/Sys/Virt/StoragePool.pm: Pod docs for
  new methods
* t/100-connect.t, t/200-domains.t, t/300-networks.t, t/400-storage-pools.t,
  t/600-interfaces.t: Test new method impls