Bug 1258: Implement DataTree partial indexing

Now the TreeNode elements are instantiated lazily per applyWrite/applyMerge/applySubtreeChange operations.
Implemented createTreeNode in TreeNodeFactory to create non recursively single node instance in TreeNode
Renamed create to createTreeNodeRecursively.

Added benchmarks project directly into the root of yangtools project.
Benchmarks project contains benchmark for testing performance of InMemoryDataTree implementation.
Tool used for benchmarks is JHM.

Change-Id: I70c9745fc9ed8751c643d9bd3e9d58be10aa4a0e
Signed-off-by: Lukas Sedlak <lsedlak@cisco.com>
Merge "Bug 1258: Implement DataTree partial indexing"