Added support for decimal grades. 
Cleaned up an-gradebook-database.php.  Deprecated function database_setup is now two functions database_init and database_alter.  The database_init function fires on a fresh install.  the database_alter function fires the necessary alterations depending on the version of the database currently installed.


git-svn-id: https://plugins.svn.wordpress.org/an-gradebook/trunk@1025530 b8457f37-d9ea-0310-8a92-e5e31aec5664