Internal node representation

[romz-pl]

In the current implementation, internal node has the same number of Key and pointers. However, the specification of B+Tree requires that number of pointers is one less than the number of keys. Moreover, the additional (surplus) key is compared during insertion process, see function LeafNode::insert.

This problem must be removed!

It is expected that the new implementation will have number of keys one less than the number of pointers, as is required by B+tree specification.