Add luacheck, update translations, replace ABMs, bug fixes (#1)

* luacheck, mt 5 translation, german translation, maintenance

* fix luacheck warnings

* Fix digital clock nodebox and texture

* Fix luacheck usage

* Add comment why fonts are not split into several lines

signs/locale/template.txt

@@ -0,0 +1,14 @@
+# textdomain: signs
+Wooden sign=
+Wooden long sign=
+Wooden direction sign=
+Poster=
+Small label=
+Label=
+Close=
+Edit=
+Title=
+Text=
+Title font=
+Write=
+(right-click to read more text)=