LDEV-61 Fixing tool sessions - all users were getting separate tool sessions. Modified ToolSessionDAO to look up either a grouped tool session or an individual tool session using the learner rather than the group (in the group cases). The "get group" code only worked for explicit groups defined in the activity object, it didn't work for a "class wide" group, so the call to the get group in the tool session lookup was replaced by an extented HQL query which look at the actual group data in the database (looking via the session table, rather than via activity).
