Some function calls to Media Foundation can fail and retrun null
pointers. They should be checked before being dereferenced to avoid a
crash.

Add note: SOLVEPNP_EPNP will be used instead of SOLVEPNP_DLS and instead of SOLVEPNP_UPNP.

* Contribute a tutorial on building for NVIDIA Tegra

* Clean-up and fixes based on feedback.

Don't run binary operations for floating-point numbers
norm() will fail with NAN result.