Add pretty printing to swaymsg

If stdout is a tty, it will pretty print unless -r (--raw) is given.

Sample outputs:

```
~/s/s/build > ./bin/swaymsg fullscreen toggle
Error: Permission denied for fullscreen toggle via IPC

~/s/s/build > ./bin/swaymsg -t get_workspaces
Workspace 3:三
  Output: DVI-I-1
  Layout: splith

Workspace 1:一 (off-screen)
  Output: HDMI-A-1
  Layout: splith

Workspace 5:五 (focused)
  Output: HDMI-A-1
  Layout: splith

~/s/s/build > ./bin/swaymsg -t get_inputs
Input device Metadot - Das Keyboard Das Keyboard
  Type: Keyboard
  Sway ID: 9456:320:Metadot_-_Das_Keyboard_Das_Keyb

Input device Wacom Intuos S 2 Pen
  Type: Tablet tool
  Sway ID: 1386:827:Wacom_Intuos_S_2

Input device Wacom Intuos S 2 Pad
  Type: Tablet pad
  Sway ID: 1386:827:Wacom_Intuos_S_2

Input device Logitech Gaming Mouse G502
  Type: Keyboard, Mouse
  Sway ID: 1133:49277:Logitech_Gaming_Mous

~/s/s/build > ./bin/swaymsg -t get_outputs
Output DVI-I-1
  Geometry: 1920x1080 @ 3840,0
  Scale factor: 1x
  Workspace: 3:三

Output DVI-D-1
  Geometry: 1920x1080 @ 0,0
  Scale factor: 1x
  Workspace: 4:四

Output HDMI-A-1
  Geometry: 1920x1080 @ 1920,0
  Scale factor: 1x
  Workspace: 5:五
```

1 files changed, 2 insertions, 10 deletions

diff --git a/sway/ipc-server.c b/sway/ipc-server.c
index 0cacc515..b5f4bb16 100644
--- a/sway/ipc-server.c
+++ b/sway/ipc-server.c
@@ -420,17 +420,9 @@ void ipc_client_handle_command(struct ipc_client *client) {
 		}
 		json_object *inputs = json_object_new_array();
 		if (input_devices) {
-			for(int i=0; i<input_devices->length; i++) {
+			for(int i = 0; i<input_devices->length; i++) {
 				struct libinput_device *device = input_devices->items[i];
-				char* identifier = libinput_dev_unique_id(device);
-				json_object *device_object = json_object_new_object();
-				if (!identifier) {
-					json_object_object_add(device_object, "identifier", NULL);
-				} else {
-					json_object_object_add(device_object, "identifier", json_object_new_string(identifier));
-				}
-				json_object_array_add(inputs, device_object);
-				free(identifier);
+				json_object_array_add(inputs, ipc_json_describe_input(device));
 			}
 		}
 		const char *json_string = json_object_to_json_string(inputs);