NuGet+Unity: include both Debug & Release DLLs and PDBs #157

It would be helpful to have both Debug and Release DLLs available in NuGet package.

For Unity, it suffices to add a define constraint DEBUG to the debug Dll. This ensures that builds use/copy the Debug DLL only when the "Development Build" checkbox is enabled. In all other cases the Release Dll will be copied.

I just tested this to confirm it still works this way, and that the editor doesn't list "Lua.dll" twice in the Assembly Definition under Assembly References.

It would also help in debugging to have the PDB files included as well. Unity will only copy them to builds if the user has "Copy PDB files" enabled: