added tests for http://code.opencv.org/issues/4011 and http://code.opencv.org/issues/3057; fixed random subset generation in both methods to increase chance for a good subset

Conflicts:
	modules/calib3d/src/stereobm.cpp

Add CV_Assert (ndisp % 8 == 0) to NEON version

removed cameraMatrix modification in the currently disabled uPnP algorithm for SolvePnP problem (http://code.opencv.org/issues/3985)

added another triangulation test case from http://code.opencv.org/issues/3461; fixed partial derivative on distortion coefficients, as http://code.opencv.org/issues/4101 suggests

- fixes the Calib3d_StereoCalibrate_C testcase.
update comment regarding cv::SVD::MODIFY_A

Similar to the problem in LevMarq, arg.inl was being used instead of
best.inl. This opened us up to a potential segfault.

temporarily use EPNP in SolvePnP instead of UPNP or DLS algorithms, since the latter two are not quite stable

Listed accesses for more functions.

Spaced methods & functions more consistently, and started documenting
which members does each method access directly or through its callers
within RHO_HEST_REFC.

- Deleted "RefC" from names of external-interface functions.
- Renamed rhorefc.[cpp|hpp] to rho.[cpp|hpp]
- Introduced RHO_HEST base class, from which RHO_HEST_REFC inherits.
- rhoInit() currently only returns a Ptr<RHO_HEST_REFC>, but in the
future it will be allowed to return pointers to other derived classes,
depending on the values returned by cv::checkHardwareSupport().

The call to rand()/random() is now a call to (unsigned)cv::theRNG().

Cholesky decomposition is stable; It is not necessary to carry it out
internally at double precision if the result will be truncated to single
precision when stored.

- Switched to the extremely fast, while simple and high-quality,
xorshift128+ PRNG algorithm by Sebastiano Vigna in "Further scramblings
of Marsaglia's xorshift generators. CoRR, abs/1402.6246, 2014" (2^128-1
period, passes BigCrush tests). Performance improved by 10% over
random().
- Added an API to allow seeding with a specified seed, rather than using
rand() or random(). This allows deterministic, reproducible results in
tests using our algorithm (although findHomography() does not yet
support passing an entropy source on its own end).

Fix the issue given NULL inlMask