v0.5.0

Complete list of improvements:

• Improve indexing structure in NodeJS:
  Instead of storing a B+Tree in memory and persisting this tree to another table, we now directly make use of the indexing capabilities of the second table and use it to store the secondaryKey -> [primaryKeys] relation.
  Our benchmarks have shown this to be superior for write accesses, while the performance dropped slightly for read accesses.
• Integrate LMDB as an alternative backend:
  LMDB can now be seamlessly integrated. Our benchmarks have shown LMDB to be superior in performance especially for large values, large transactions and indices, even outperforming the previous in-memory B+Tree.
  Moreover, LMDB is a synchronous backend, allowing to reduce the number of async/await operations dramatically (while still maintaining the same API to the outside).
• Add new benchmarks and output CSV compatible format instead of text.
• Restructuring of LMDB backend, usage of native dup keys for LMDB indexes.
• Automatic resizing of database.

If the autoResize option is enabled, the database will automatically resize itself if needed by minResize (default is 1GB).