fixed an issue where certain GET requests would be performed more often then needed and added tests for the requestservice (not everything tested yet)

Replaced Http with HttpClient

Closes #150 

Switched to storing requests based on UUID, generalized UUIDIndexReducer to work with any type of index

cleaned up remotedata for a better separation of concerns, moved statuscode and errormsg in to RemoteDataError object, moved pageInfo to PaginatedList object in the payload

Increase test coverage