[new index structure] BTreeNode is superclass for MemoryBTreeNode and BTree constructor requires BTreeNodeFactory.
Added PagedBTreeNode with proof-of-concept buffer manager, tests fail.
[new B+ tree] Fixed some of the BTree tests.
[new index structure] PagedBTreeNodes will get dirty, BTreeBufferManager is an interface.
[new index structure] BTreeStorageBufferManager updated: does not yet actually use storage but passes the tests.
[new index structure] BTreeStorageBufferManager uses its storage now. Parent reference of nodes is the main obstacle before using the buffer manager in all test cases. Basic test cases pass.
[new B+ tree] Removed calls to getParent() from insert/delete methods. Fixed a couple of tests.
Merge remote-tracking branch 'origin/split-BTree-node' into split-BTree-node
[new B+ tree] Replaced calls to parent in current code.
[new B+ tree] Cleanup and extra documentation.
[new B+ tree] Abstracted the node factory by creating 2 types of trees, PagedBTree and MemoryBTrees.
The paged BTrees use a BTreeBufferManager for reading/writing pages.
[new B+ tree] Added some implementation to the BTree index.