Added unit tests covering parsing of Json for all the pieces of the project.json
Added a RawRuntimeOptions to Project and made Executable deserialize that into the runtimeOptions of runtimeconfig.json
Added tests to cover copying runtimeoptions during dotnet build.
dotnet-build will produce a deps file for portable builds, and will now
create "runnable" outputs for RID-less targets
the outputs won't actually be runnable today because we need corehost
changes and to generate a deps.json file for corehost to use.
