Fisheye Camera for PyTorch3D

Summary:
1. A Fisheye camera model that generalizes pinhole camera by considering distortions (i.e. radial, tangential and thin-prism distortions).

2. Added tests against perspective cameras when distortions are off and Aria data points when distortions are on.

3. Address comments to test unhandled shapes between points and transforms. Added tests for __FIELDS, shape broadcasts, cuda etc.

4. Address earlier comments for code efficiency (e.g., adopted torch.norm; torch.solve for matrix inverse; removed inplace operations; unnecessary clone; expand in place of repeat etc).

Reviewed By: jcjohnson

Differential Revision: D38407094

fbshipit-source-id: a3ab48c85c496ac87af692d5d461bb3fc2a2db13

Author: davidsonic