Opencast Database documentation doesn't specify "alter" rights for "matterhorn"
Steps to reproduce
Even though a current pull  will reverse the need for "matterhorn" to have "alter" rights to create tables. It needs "alter" rights to upgrade the database using the upgrade ddl scripts.
Steps to reproduce:
1. following GRANT instructions in Opencast documentation 
2. log into a 1.6 db as matterhorn and attempt to run the upgrade script
Actual Results: "matterhorn" user does not have "alter" rights.
Expected Results: "matterhorn" user is able to upgrade the database
Since it is already recommended to grant "matterhorn" CREATE and DROP , it makes sense to also grant it ALTER rights so it can run the upgrade scripts.
It's dangerous to allows Matterhorn user alter rights. Matterhorn could unintentionally alter the table via the JPA code which could lead to data loss. Its safer to require the root user to alter Opencast tables to ensure intentional action.