This commit contains some miscellaneous Windows fixes discoverd while
integrating PGV with Envoy

- Remove incorrect comment about including "validate/validate.proto"
- Always make sure WIN32 is defined when compiling *.pb.validate.cc
- Include <google/protobuf/message.h> and <google/protobuf/util/time_util.h>
  in the *.pb.validate.cc file instead of validate.h. This is because
  these headers include <windows.h> which defines many macros (e.g.
  DELETE). If this header is then included before any code that has
  symbols by the same name, it will fail to compile
- Use std::unordered_map instead of std::map because we don't care about
  traversing the keys in order
- Remove the complicated windows.ps1 set up script and just run the
  bazel command

Signed-off-by: Amin Jamali <ajamali@pivotal.io>