implemented _search_shards API support
implemented get repository API
added bwc for get repository and search_shards
Merge branch 'develop' into feature/get-repository

Conflicts:
	src/Nest/IElasticClient.cs
	src/Nest/Nest.csproj
	src/Tests/Nest.Tests.Integration/IntegrationSetup.cs
Merge branch 'feature/get-repository' into develop