0.2.51.30 (EXPERIMENTAL) - Transmission mesh types

Added 3 transmission mesh modes:

Synchromesh (default): Easier speed matching, allowing higher gear steps in some cases. Bigger and more expensive transmissions. Slower to engage gears.

Constant mesh: Requires precise speed matching by the driver. Small and cheap transmissions.

Slide mesh: WWI option pre synchromesh invention and constant mesh use on tanks. The same behaviour as constant mesh but bigger and cheaper.

These aren't limited by era yet.

Synchromesh goes: declutch > shift > reclutch
Constant mesh and slide mesh require the new double declutching: declutch > neutral > clutch > speedmatch > declutch > shift > reclutch

Your transmissions will be set to synchromesh and wont change size.

Other changes

• The driver now only upshifts if the vehicle is capable of accelerating in the current gear and the next gear would also accelerate.
• The driver now only downshifts if the engine speed drops below its operating rpm (+ an estimated drop from shifting) and the current gear isn't capable of accelerating.
• Engine 'Downshift' renamed to 'Operating speed'
• Speed match threshold increased from 50rpm to 100rpm. This gets bumped up to 250rpm if the engine is about to stall.
• Engine friction is now higher in earlier eras and track resistance has been reduced further. Should help with speed matching issues.
• Fixed vehicles not upshifting in reverse.
• Removed the failed shift notification