Move base.nix and me.nix from roles to fragments

fragments/base.nix

@@ -9,7 +9,7 @@
   # networking.hostName = "nixos"; # Define your hostname.
   # Pick only one of the below networking options.
   # networking.wireless.enable = true;  # Enables wireless support via wpa_supplicant.
-  networking.networkmanager.enable = true;  # Easiest to use and most distros use this by default.
+  networking.networkmanager.enable = lib.mkDefault true;  # Easiest to use and most distros use this by default.
 
   # List packages installed in system profile. To search, run:
   # $ nix search wget
@@ -29,8 +29,8 @@
   ];
 
   programs.gnupg.agent = {
-    enable = true;
-    enableSSHSupport = true;
+    enable = lib.mkDefault true;
+    enableSSHSupport = lib.mkDefault true;
   };
 
 }