ClosureTable 2.1.5

Fixes:

1. #27, database table prefix led to wrong closure table name.
2. #25, wrong behaviour happened while moving a descendant to a new ancestor by using moveTo().
3. #42, #37, #32, wrong position was set when an entity was moved or created.
4. #43, position was updated even if a user tried to move an entity to the same ancestor it already belonged to.