A few improvements

[Robertleoj]

• No focal length estimate required
• synthetic dataset available to run notebooks
• if pnp fails, discard the frame - have to support None in outputs
• Add more tests
• Perform the spline distortion in stereographic space
• Better mechanic to auto-select an FOV
• Change spline regularization to be a penalty on the numerical third derivative
• Drastically speed up spline solves
• Guide has a better image set
• Use spline-native calculations for computing the alpha remap models instead of relying on the opencv seed