v2.6.0: Big updates and optimizations

General updates

• Added optional in-memory structure (new default)
• Added optinal in-memory writes queue (new default)
• optimized writes queue (handles ~600,000 writes per second, only limitation is ram)
• Added "kill_db" which flushes all queued writes into the database before killing the program.
• Created tests.py to test various database functions and their speeds.
• Structure format is now a Structure Write-Ahead Log (SWAL). This is extremely similar to a regular WAL, except this is not all database transactions, this is all transactions to the structure and it is the only way the structure can be interacted with. When nahcrofDB starts, the entire structure will be "built" in memory (if st_store_method is set to "memory")
• Databases no longer track total writes or reads made.