Added composer.json and the composer autoloader include
Removed xtc_db_data_seek in preparation for the switch to doctrine, as it is a db driver specific feature and thus not supported by doctrine
Rewrote the xtc_db_* functions to use doctrine and fixed all code, that didn't use the xtc database wrapper.
Added an executed 'composer.phar install' command to the install requirements
Changed the installer to automatically install composer and execute 'composer.phar install'