Remove mysql - this should fix issue 29 - namely removal of most mysql_ function calls see issue #29

This pull request .... :

 1. Removes the hard dependency on mysql_ outside of the setup folder.
 2. Introduces support for using SQLite as the database for XOT
 3. Changes the default install to use SQLite (see config.php) - a database will be created in the system's temporary directory by default if it does not exist; meaning there should be no need to create a database or setup MySQL in order to use XOT. Edit config.php to easily switch back to MySQL.
 4. Removes a number of incorrect data escapings (e.g. use of mysql_real_escape_string() around parameters being passed to mail()) and should make the code base immune from SQL Injection issues.
 5. Make it easier to support different SQL backends in the future (e.g. Oracle or MSSQL).
 6. Should ease any transition to post PHP v5.5 (5.5 deprecated the mysql extension, presumably a future version may not have support for the 'mysql_' functions). 


All database calls are now made through the db_query() or db_query_one() functions. 

See also issue #29