Igibson

Bug-fixes
- pybullet retore state
- adjacency ray casting
- link CoM frame computation
- sem/ins segmentation rendering
- simulator force_sync renderer
- material id for objects without valid MTL
- Open state checking for windows
- BehaviorRobot trigger fraction out of bound
- BehaviorRobot AG joint frame not at contact point

Improvements
- Refactor iG object inheritance
- Improve documentation
- Improve sampling
- scene caches support FetchGripper robot
- BehaviorRobot action space: delta action on top of actual pose, not "ghost" pose
- Upgrade shader version to 460
- Minify docker container size

New Features
- VR Linux support
- GitHub action CI

Changelog:

- Fix semantic segmentation and instance segmentation bug
- Fix a material handling bug and improve readability

Changelog:

- Added support for FetchGripper robot
- Integrate FetchGripper robot for BEHAVIOR tasks
- Miscellaneous bug fixes

Major update to iGibson to reach iGibson 2.0, for details please refer to our [arxiv preprint](https://arxiv.org/abs/2108.03272).

- iGibson 2.0 supports object states, including temperature, wetness level, cleanliness level, and toggled and sliced states, necessary to cover a wider range of tasks.
- iGibson 2.0 implements a set of predicate logic functions that map the simulator states to logic states like Cooked or Soaked.
- iGibson 2.0 includes a virtual reality (VR) interface to immerse humans in its scenes to collect demonstrations.

The version of iGibson to support Behavior Challenge. For more information please visit: http://svl.stanford.edu/behavior/challenge.html