VirStorageVol implementation

VirStorageVol implementation.Adding StorageVolCreateXMLFromFile, StorageVolCreateXML,Delete ,Free and appropriate tests

Adding GetInfo and test

Adding VirStorageVolGetKey, VirStorageVolGetName and appropriate tests

Adding VirStorageVolGetPath and appropriate test

Adding VirStorageVolGetXMLDesc and appropriate test

Adding VirStorageVolLookupByKey,VirStorageVolLookupByName, VirStorageVolLookupByPath and appropriate tests

Adding Resize,Wipe and WipePattern plus appropriate integration tests
VirSecret implementation thanks @dorzheh

SecretDefineXMLFromFile and SecretDefineXML

LookupSecretByUUIDString and LookupSecretByUsage

Constants  virSecretUsageType

Free and Undefine

GetUUID and GetUUIDString

GetUsageID , GetUsageType and GetXMLDesc

Integration tests
Add VirDomain.GetCPUStats and VirDomain.GetInterfaceParameters
Added ListAllInterfaces and integration test
Added VirConnectListAll*, tests/integration tests and constants
Merge pull request #24 from dorzheh/master

Added VirConnectListAll*, tests/integration tests and constants
Basic VirStream implementation
Add VirDomainScreenshot
Add VirDomainSendKey.

(Test excluded because test connection driver unsupported)
Extend TestDomainScreenshot, remove SendKey test
Rename VirStream's Finish() to Close() for io.Closer
remove png test
Add BlockStatsFlags
add TestIntegrationDomainBlockStatsFlags