Idle handling for dpms/lockscreen et al

Swayidle handles idle events and allows
for dpms and lockscreen handling. It also
handles systemd sleep events, and can
raise a lockscreen on sleep

Fixes #541

swayidle/meson.build

@@ -0,0 +1,17 @@
+threads = dependency('threads')
+
+executable(
+	'swayidle', [
+		'main.c',
+	],
+	include_directories: [sway_inc],
+	dependencies: [
+		client_protos,
+		wayland_client,
+		wayland_server,
+		wlroots,
+		swayidle_deps,
+	],
+	link_with: [lib_sway_common, lib_sway_client],
+	install: true
+)