some syntax fixes
setup development version
make use of the WordPress Shortcode API

Make use of the WordPress Shortcode API (see http://codex.wordpress.org/Shortcode_API) in order to fix a compatibility issue with WordPress 4.0.1.
keep wrapper settings in a global variable for further use
Bugfix: Don't shutdown the whole website, if the plugin is improperly configured.

If the plugin is improperly configured, the whole website is shutdown via "wp_die()". Only an error message should be displayed on the page / article in place of the shortcode instead.
readme files modified
Bugfix: Show correct home path of the WordPress installation on the plugins admin page.

If WordPress is not installed in the root folder of the domain, a wrong path of the WordPress installation is shown on the admin page of the plugin. This may confuse users about the correct script path.

This problem does not occur, if get_home_path() is used to determine the path of the WordPress installation (see http://codex.wordpress.org/Function_Reference/get_home_path).
Bugfix: Show correct plugin version number on the plugins admin page.

A wrong version number of the plugin is shown on the plugins admin page. The correct versions number should be obtained via get_plugin_data() - see http://codex.wordpress.org/Function_Reference/get_plugin_data
added helper scripts for internationalization
updated translation files
translated any source code comments into English