Physics rework v8.3b

A regular version of physics

Changes:
Reworked cabin behavior
Reworked seat behavior
New recommended settings

Recommended settings for v8.3b (can be changed in console or in config files):
g cam physics value "1.0" (DEFAULT)
g cam physics "1" (DEFAULT)

g_cabin_suspension_stiffness "1.3" (see ATTENTION below!)
g_suspension_stiffness "0.3"
g_trailer_stability "0.5" (DEFAULT)
g_truck_stability "0.3"

g_brake_intensity "1.0" (DEFAULT)

residual_travel[] in chassis defs: 0.10 and 0.088 (DEFAULT).