Based on patch from Arch additionally using system's Shaders/

Resulting paths:
/usr/share/higan/{Database,Firmware,Shaders,Templates}
~/higan/ -> ~/.local/share/higan/Systems

Templates+Systems can be changed in ~/.config/higan/paths.bml and
does not disrupt existing configurations. Shaders will use default
~/.config/higan/Shaders over system's if it exists.

https://bugs.gentoo.org/828108
--- a/higan-ui/higan-ui.cpp
+++ b/higan-ui/higan-ui.cpp
@@ -44,9 +44,8 @@
   }
   if(!directory::exists(Path::templates)) {
-    Path::templates = {Path::userData(), "higan/"};
-    directory::create(Path::templates);
+    Path::templates = {Path::sharedData(), "higan/Templates/"};
   }
   if(!directory::exists(Path::data)) {
-    Path::data = {Path::user(), "higan/"};
+    Path::data = {Path::userData(), "higan/Systems/"};
     directory::create(Path::data);
   }
--- a/higan-ui/menus/settings.cpp
+++ b/higan-ui/menus/settings.cpp
@@ -78,4 +78,6 @@
 
   string location{Path::settings, "Shaders/"};
+  if(!directory::exists(location))
+    location = string{Path::sharedData(), "higan/Shaders/"};
 
   if(settings.video.driver == "OpenGL 3.2") {
--- a/icarus/icarus.cpp
+++ b/icarus/icarus.cpp
@@ -9,6 +9,5 @@
   if(inode::exists(location)) return location;
 
-  directory::create({Path::userData(), "icarus/"});
-  return {Path::userData(), "icarus/", name};
+  return {Path::sharedData(), "higan/", name};
 }