add results API call

[Groostav]

As a volition API user I want an api to call to get me the optimization results so that I can present these results to the user

This issue is to add an ability for API users to fetch the result from an optimization.

As per https://groups.google.com/forum/#!topic/protobuf/pb4DaQLHPu8,

the max size is 64MB (larger is possible but not recomended)

I propose we break it down into a kind of pagination system via a stream.

service Optimizer {
  rpc getOptimizationSummary(SummaryRequestDTO) returns OptimizationSummaryResponseDTO
  rpc getOptimizationResults(ResultsRequestDTO) returns stream OptimizationResultPageDTO
}