Release v0.18.0

[sebcrozet]

Added

• Add the accessor RapierContext::physics_scale() to read the physics scale
  that was set when initializing the plugin.
• Add RapierConfiguration::force_update_from_transform_changes to force the transform
  updates even if it is equal to the transform that was previously set. Useful for
  rollback in networked applications described in #261.
• Add Collider::trimesh_with_flags to create a triangle mesh collider with custom pre-processing
  flags.

Fix

• Reset the ExternalImpulse component after each step automatically.
• Fix transform_to_iso to preserve identical rotations instead of
  converting to an intermediate axis-angle representation.
• Fix internal edges of 3D triangle meshes or 3D heightfields generating invalid contacts
  preventing balls from moving straight. Be sure to set the triangle mesh flag
  TriMeshFlags::MERGE_DUPLICATE_VERTICES when creating the collider if your mesh have duplicated
  vertices.

Modified

• Rename AABB to Aabb to comply with Rust’s style guide.