fixed build issues
- inlude files weren't set up correctly. this only became a problem
  because of the use of templates, i think.
- project files should now show include files as well. haven't tested VS
  proj files.
- moved ScreamMain to Engine. i *think* i've made up my mind about this.
- renamed TemplatePlugin/PluginEntry.cpp to
  TemplatePlugin/TemplatePlugin.cpp. this was a mistake in the previous
  commit. i did not mean to check it in as PluginEntry.cpp