support eltwise sum with different number of input channels in CUDA backend

* add shortcut primitive

* add offsets in shortcut kernel

* skip tests involving more than two inputs

* remove redundant modulus operation

* support multiple inputs

* remove whole file indentation

* skip acc in0 trunc test if weighted

* use shortcut iff channels are unequal

Enable cuda4dnn on hardware without support for __half

* Enable cuda4dnn on hardware without support for half (ie. compute capability < 5.3)

Update CMakeLists.txt

Lowered minimum CC to 3.0

* UPD: added ifdef on new copy kernel

* added fp16 support detection at runtime

* Clarified #if condition on atomicAdd definition

* More explicit CMake error message

Fix implicit conversion from array to scalar in python bindings

* Fix wrong conversion behavior for primitive types

  - Introduce ArgTypeInfo namedtuple instead of plain tuple.
    If strict conversion parameter for type is set to true, it is
    handled like object argument in PyArg_ParseTupleAndKeywords and
    converted to concrete type with the appropriate pyopencv_to function
    call.
  - Remove deadcode and unused variables.
  - Fix implicit conversion from numpy array with 1 element to scalar
  - Fix narrowing conversion to size_t type.

* Fix wrong conversion behavior for primitive types

  - Introduce ArgTypeInfo namedtuple instead of plain tuple.
    If strict conversion parameter for type is set to true, it is
    handled like object argument in PyArg_ParseTupleAndKeywords and
    converted to concrete type with the appropriate pyopencv_to function
    call.
  - Remove deadcode and unused variables.
  - Fix implicit conversion from numpy array with 1 element to scalar
  - Fix narrowing conversion to size_t type.·
  - Enable tests with wrong conversion behavior
  - Restrict passing None as value
  - Restrict bool to integer/floating types conversion

* Add PyIntType support for Python 2

* Remove possible narrowing conversion of size_t

* Bindings conversion update

  - Remove unused macro
  - Add better conversion for types to numpy types descriptors
  - Add argument name to fail messages
  - NoneType treated as a valid argument. Better handling will be added
    as a standalone patch

* Add descriptor specialization for size_t

* Add check for signed to unsigned integer conversion safety

  - If signed integer is positive it can be safely converted
    to unsigned
  - Add check for plain python 2 objects
  - Add check for numpy scalars
  - Add simple type_traits implementation for better code style

* Resolve type "overflow" false negative in safe casting check

 - Move type_traits to separate header

* Add copyright message to type_traits.hpp

* Limit conversion scope for integral numpy types

  - Made canBeSafelyCasted specialized only for size_t, so
    type_traits header became unused and was removed.
  - Added clarification about descriptor pointer

Add lightweight IE hardware targets checks

nGraph: Concat with paddings

Enable more nGraph tests

Restore FP32->FP16 for GPU plugin of IE

try to fix buildbot

Use lightweight IE targets check only starts from R4

G-API: Fix G_TYPED_KERNEL_M macro

* Fix G_TYPED_KERNEL_M macro

* Fixes

* Fix windows build
* Fix doxygen

* Added several macros

* Add overloads for G_TYPED_KERNEL

* Added java code for meanshift and optical_flow

* added java code for module video

* added appropriate spaces in codes

* converted absolute path to command line arguments

* added spaces at appropriate places

Python code examples for file IO in xml and yml format

* Initial "Pythonization" of file_input_output.cpp

* Moved file_input_output.py to correct location

* Nearly done Pythonizing file_input_output.cpp

* Python equivalent of file_input_output.py created

* Started Pythonizing camera_calibration.cpp

* Completed Python tutorial/sample code for file_input_output

* Resolved whitespace issues

* Removed tabs in file_input_output.cpp

* Patched import order and wrapped code in main function

* Changed string to docstring format in help file

* Updated link to Python example code

* core: fix intrin_cpp, allow to build modules with SIMD emulator

* core(arithm): fix v_zero initialization

* core(simd): 'strict' types for binary/bitwise operations

* features2d: avoid aligned load issue in GCC 5.4 with emulated SIMD

* core(simd): alignment checks in SIMD emulator

* Changed plus operator to os.path.join()

* Remove '/' from PATH

When building OpenCV as a sub-project using cmake's add_subdirectory()
the OpenCV's build options would be overwritten to its default
state. With cmake 3.13+ the CMP0077 policy, option() honors previous
definitions via set().

dl functions are provided by all glibc-based systems (GNU/Linux, but
also GNU/Hurd, GNU/kFreeBSD)