Add first version of database model

We have to use now Hibernat 3.4.0.GA instead of the newest version, because of problems with the JPA 2.0 and OneToMany Mapping
Implement changes from meeting
Implement user are member of a group
Implement news system
Implement user message system
Start redesign the database - Add instance and roles
Add permission tables
Add user table and its indecies
Add message system tables
Add instance admin table
Add lecture and its leader
Implement group tables
Add news table
Add task tables
Add material tables
Add submission tables
Fix for mysql 5.5 and add message to a submission
Add sample solution tables
Rename tables for consistent naming
Add missing relation between sample solution an its file