Point table initialisation for manually added student

[jprk]

There seems to be an error in the initialisation of the points table when adding a new student. By default we assume that after enrolling a new student into the system the corresponding entries in the points table are automatically created and set to PTS_NOT_CLASSIFIED. This works for batch imports -- it is implemented in ImportBean.class.php, method doSave() --, but it is however not true for students who are created and enrolled manually.

The issue affects also evaluation of home works: If a student submits a solution (PDF, ZIP file) to a subtask and the points for the subtask are not initialised, she/he is not displayed in the list of submitted home works.

We have two separate issues here:

1. the logic responsible for enrolling a student shall automatically handle the initialisation of points table
2. when creating or deleting a subtask, the points table shall be also altered accordingly.

Affected methods: only ImportBean::doSave() and StudentBean::doSave(), probably.