Make it easier to define custom rule character(s) in rules.lua

* Improve presentation of what lines are ignored or not. * Add actual extended line information output (when selected).

Improved the finding empty vehicle code further.

Duplicate emptiest vehicle when adding a new vehicle to a line.

General minor updates, including workload balancing in general.

Documentation fixes.

Documentation updates.

Description fixes.

CARGO update - extensive updates/upgrades throughout. Can now manage all line types. In-game settings menu available.

Change state to version 3 to hopefully invalidate older saves with possible state issues.