adding protobuf compiler to dependencies, used in branches
install protoc thru nuget
Merge pull request #1164 from Project-OSRM/appveyor_nuget

Install protoc on both Travis and AppVeyor.
Initial commit for protobuf descriptor.
Update cmake file to generate protobuf files and create a dependancy
Add protobuf file.
Update ViaRoutePlugin to use protobuf descriptor.
Add protobuf to description table.
Create functions for Polyline Compressor and Description Factory to return string and vector<string> values.
Intermediate result for adding data to protobuf response.
Add protobuf message Route. In response message create main and additional routes.
Add alternative way description
Add route names.
add Hint.
Add RouteInstructions
Pass vector as reference.
Refactoring. Move common parts to Descriptor.h
Code review fixes