Orthographic Camera Support

[Skylion007]

Motivation and Context

• It enables orthographic camera support in Habitat-Sim from Habitat-Lab. Adds a new field to Visual Sensors for SENSOR_SUBTYPE. Also working on adding a demo to examples/example_visualization.

Need feedback on the API. There is currently no way to set the default zoom in the sensor spec for Habitat_Sim. This may need to be changed.

How Has This Been Tested

CI and locally

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist

• [X] My code follows the code style of this project.
• [X] My change requires a change to the documentation.
• [X] I have updated the documentation accordingly.
• [X] I have read the CONTRIBUTING document.
• [X] I have completed my CLA (see CONTRIBUTING)
• [X] I have added tests to cover my changes.
• [X] All new and existing tests passed.

[mathfac]

@Skylion007, does this PR still makes sense? What about merge it in several days before we do config refactoring.