Helps with discovery and setup of physics solver settings, in a specific
project settings section for both 2D and 3D.
Other changes for cleanup:
-Removed unused space parameters in 3D
SPACE_PARAM_BODY_ANGULAR_VELOCITY_DAMP_RATIO
SPACE_PARAM_CONSTRAINT_DEFAULT_BIAS
-Added custom solver bias for Shape3D (same as Shape2D)
-Improved documentation for solver settings
For the time being we don't support writing a description for those, preferring
having all details in the method's description.
Using self-closing tags saves half the lines, and prevents contributors from
thinking that they should write the argument or return documentation there.
