MXS-1942: Use MaxScale version in MaxCtrl

Displaying the MaxScale version helps identify which package the
executable was bundled with. As the MaxCtrl source is a part of MaxScale,
there's no need for separate versioning.

maxctrl/lib/core.js

@@ -14,7 +14,9 @@
 var fs = require('fs')
 var program = require('yargs');
 
-const maxctrl_version = '1.0.0';
+// Note: The version.js file is generated at configuation time. If you are
+// building in-source, manually create the file
+const maxctrl_version = require('./version.js').version;
 
 program
     .version(maxctrl_version)

maxctrl/lib/version.js.in

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2020-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+exports.version = "@MAXSCALE_VERSION@"