:green_heart: Fix build on appveyor

[ToruNiina]

The following changes make it compiles on appveyor.

• Define some macros through CMakeLists.txt
  • NOMINMAX
  • to prevent macro definition in <windows.h>.
  • GSL_DLL
  • required to link GNU Scientific Library on Windows.
• Rename (add prefix POLICY_) enumerators in ReactionRule::policy_type
  • to avoid name conflict with predefined macro, STRICT.
• Remove using namespace ecell4::egfrd from python_api/egfrd.cpp
  • the reason is a bit complicated. please see the commit message.
• Update greens_functions
  • almost the same reason as above.