Add Lua functions to query keyboard bindings and remove individual keybinds

Add core script file that defines possibility of rebinding keyboard commands to a different key
Enable the execution of global customization scripts
Make `scene_helper.lua` a script automatically included in the ScriptScheduler

scripts/common_scripts.lua

@@ -0,0 +1,20 @@
+openspace.documentation = {
+    {
+        Name = "rebindKey",
+        Arguments = "string, string",
+        Documentation = "Rebinds all scripts from the old key (first argument) to the " ..
+        "new key (second argument)."
+    }
+}
+
+openspace.rebindKey = function(old_key, new_key)
+    local t = openspace.getKeyBinding(old_key)
+    openspace.clearKey(old_key)
+    for _, v in pairs(t) do
+        if v["Remote"] then
+            openspace.bindKey(new_key, v["Command"])
+        else
+            openspace.bindKeyLocal(new_key, v["Command"])
+        end
+    end
+end