Vector Search in SDK Docs - phase I

Vector search is initially being introduced to the SDKs at @Stability.Volatile status 

At this time, it will be included with the Search docs, sharing as it does a common interface - 

SearchRequest request = SearchRequest         .create(VectorSearch.create(VectorQuery.create("vector_field", vectorQuery)));

At some time in the future - during or after the SDK docs IA re-org - a separate Vector Search doc will be created for each SDK.