Version 2.21

Version	2.21.0
Release Date	2025-01-18
Author	Albert Ball
Changelog	Routes can now be truncated between two signals, rather than just from or to a single signal. Maximum speed of a train can now be changed mid-service, using the new 'cms' timetable command. Fixed a bug where a follow-on service had a headcode but no description, and had an error, the validator would additionally report a non-existent error in the headcode. Updated the session check function to account for larger railways, as some of the function limits had been reached.