* Rewrite polar transformations

- A new wrapPolar function encapsulate both linear and semi-log remap
- Destination size is a parameter or calculated automatically to keep objects size between remapping
- linearPolar and logPolar has been deprecated

* Fix build warning and error in accuracy test

* Fix function name to warpPolar

* Explicitly specify the mapping mode, so we retain all the parameters as non-optional.

Introduces WarpPolarMode enum to specify the mapping mode in flags

* resolves performance warning on windows build

* removed duplicated logPolar and linearPolar implementations

* lab_tetra squashed

* initial version is almost written

* unfinished work

* compilation fixed, to be debugged

* Lab test removed

* more fixes

* Luv2RGBinteger: channels order fixed

* Lab structs removed

* good trilinear interpolation added

* several fixes

* removed Luv2RGB interpolations, XYZ tables; 8-cell LUT added

* no_interpolate made 8-cell

* interpolations rewritten to 8-cell, minor fixes

* packed interpolation added for RGB2Luv

* tetra implemented

* removing unnecessary code

* LUT building merged

* changes ported to color.cpp

* minor fixes; try to suppress warnings

* fixed v range of Luv

* fixed incorrect src channel number

* minor fixes

* preliminary version of Luv2RGBinteger is done

* Luv2RGB_b is in progress

* XYZ color constants converted to softfloat

* Luv test: precision fixed

* Luv bit-exactness test added

* warnings fixed

* compilation fixed, error message fixed

* Luv check is limited to [0-2,0-2,0-2] by XYZ

* L->Y generation moved to LUT

* LUTs added for up and vp of Luv2RGB_b

* still works

* fixed-point is done, works at maxerr 2

* vectorized code is done, 2x slower than original

* perf improved by 10%

* extra comments removed

* code moved to color.cpp

* test_lab.cpp updated

* minor refactoring

* test added for Luv2RGB

* OCL Luv2RGB_b: XYZ are limited to [0, 2]; docs updated

* Luv2RGB_b rewritten to universal intrinsics

* test_lab.cpp moved to luv_tetra branch

Added documentation to the Subdiv2D documentation, based on the previous
C API.

fixes #5689

Rewrite the note on HoughCircles documentation to make it more clear

Add note to clarify that the output vector of found circles is sorted by
descending order of centres accumulator values.

Also delete reductant lines on the HoughCircles documentation.

Added comments to hough circles function.

Added comments to icvhoughgradient

Misalignment in line 1183 corrected

- disabled doxygen tree
- enabled doxygen enum listing
- added imgproc reference to main page
- enabled BiB support
- chenged doxygen root page format

Add Triangle method for automatic threshold computation next to the existing
Otsu's method. Triangle deals better with images whose histogram does not
contain dominant peak.

See paper Zack GW, Rogers WE, Latt SA.: Automatic measurement of sister
chromatid exchange frequency. J Histochem Cytochem. 1977 Jul;25(7):741-53.

Fixed doc for Bug #3887

(cherry picked from commit b027eac1)

Apart from not displaying the table, it breaks the doc build of https://github.com/Itseez/opencv_contrib/pull/70.

removed optim module; moved its functionality to core and photo modules; moved drawing functions from core to imgproc. Removed FilterEngine etc. from public API

Corrected crashing in Python bindings while using LSD_REFINE_NONE flags
Corrected not drawing lines in drawSegments and compareSegments in Python bindings

Updating missed defines in documentation. The new defines (in imgproc.hpp) state they have a prefix of COLOR instead of CV.