Move api_version.lua into examples

As this script is more usable for developers then for 'normal' users I moved it into examples.

examples/api_version.lua

@@ -0,0 +1,27 @@
+--[[
+    This file is part of darktable,
+    Copyright 2014 by Tobias Jakobs.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+]]
+--[[
+darktable script to show the Lua API version in the preferences
+
+USAGE
+* require this script from your main lua file
+]] 
+local dt = require "darktable"
+
+local result = dt.configuration.api_version_string
+dt.print_error("API Version: "..result)