Version 4.3.0

Added

• explicit thread pool management
• more sections in manual: on history and diff files and writers

Fixed

• issue with pyosmium scripts not properly returning on Windows

Changed

• updated to libosmium 2.23.0
• use per-reader/writer thread pools instead of libosmium's global pool
• replace boost iterator with simple C++ iteration tools from stdlib
• drop dependency on boost