addresses #18
addresses #17
* create an english translation of the templates
* change the template directory for smarty depending on the language
* move existing templates to german subdirectory
* the config file handling code has been moved to a separate file which is shared between normal and AJAX code
* the config file existence is checked and a well formatted error message is sent if it doesn't exist
* Makefile creates/updates po/davadmin.pot, .po, and .mo files
* admin/i18n.inc.php sets the locale and puts it in the session
* admin/common.inc.php and admin/getgroups.php use admin/i18n.inc.php
* po/pot.sed replaces generated header of po/davadmin.pot