Build velia daemon

Introduce package for velia, configure build and systemd services.
Removes czechlight LEDs boot service.

Change-Id: I84d724918a3a6c7654eb113abce4d7068d7770a6
Co-authored-by: Jan Kundrát <kundrat@cesnet.cz>
diff --git a/.gitmodules b/.gitmodules
index fef9a47..b249b40 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -10,3 +10,6 @@
 [submodule "submodules/gammarus"]
 	path = submodules/gammarus
 	url = ../gammarus
+[submodule "submodules/velia"]
+	path = submodules/velia
+	url = ../velia/