Merge pull request #60 from ivan-shaporov/dev

Cache MediaServicesEndpoint using azureMediaServicesEndpoint parameter of AzureMediaServicesClassFactory constructor as the key.
Audio preset test, job progress test and introducing folders for entities and collections
Merge branch 'dev' of https://github.com/WindowsAzure/azure-sdk-for-media-services into dev
Fix OrderBy issue.
Merge branch 'dev' of https://github.com/WindowsAzure/azure-sdk-for-media-services into dev