Bucket stats

## Overview

This pull request includes functionality for users to view some stats on their individual buckets including:

```
BranchPageCount    - The number of branch pages.
LeafPageCount      - The number of leaf pages.
OverflowPageCount  - The number of pages extended for large keys/values.
KeyCount           - The total number of keys.
MaxDepth           - The depth of the B+tree.
```