[new index structure] BTreeIterator traverses inner and leaf nodes in a BTree in pre-order
[new index structure] Nodes are removed from the buffer manager when they are removed during merge.
[new index structure] anotherDeleteTest throws ArrayIndexOutOfBoundsException
[new index structure] BTreeStorageBufferManager now implements maximum cache size for clean nodes.
[new index structure] BTreeStorageBufferManager counts number of page-writes and reads.
[new index structure] Added PageUsageStats performance test that compares old and new index based on their page usage.
[new B+ tree] Finished basic operations for non-unique/unique trees.
Merge branch 'new-index-structure' into unique-non-unique-trees

Conflicts:
	src/org/zoodb/internal/server/index/BTreeIndex.java
	src/org/zoodb/internal/server/index/btree/BTree.java
	src/org/zoodb/internal/server/index/btree/BTreeNode.java
	src/org/zoodb/internal/server/index/btree/BTreeUtils.java
	src/org/zoodb/internal/server/index/btree/MemoryBTreeNode.java
	src/org/zoodb/internal/server/index/btree/PagedBTreeNode.java
	tst/org/zoodb/test/index2/btree/TestBTree.java
	tst/org/zoodb/test/index2/btree/TestBTreeStorageBufferManager.java
	tst/org/zoodb/test/index2/btree/TestNode.java
	tst/org/zoodb/test/index2/btree/TestNonUnique.java
[new B+ tree] Finished merging tests.
[new B+ tree] Fixed shifting left with index method.
[new B+ tree] Cleanup and comments.