Create initial native binding using rocksdb

[shuse2]

Motivation

• In order to use more feature from rocksdb, new native binding was required
• Sparse merkle tree calculation requires good performance, which cannot be achieved by node.js

Tasks

• Implement initial sparse merkle tree, database and state db implementation #2
• Create release automation #3
• Add smt.prove logic #9
• Add smt.verify logic #10
• Add clone method to InMemoryDatabase #12

[milenagojkovic]

All tasks are closed, closing the epic.