added handling of camera parameters estimation errors (#3122)
added 'cmath' include
fixed Windows build
removed trailing whitespaces causing warnings
updated docs
fixed include for Windows
fixed docs
split mog sources
refactored MOG algorithm

converted it to abstract interface
refactored MOG2 algorithm
refactored GMG algorithm
refactored FGD algorithm
made module dependency optional
updated documentation
Solve the problem seen when using recent versions of CMake (such as 2.8.11): OpenCVConfig.cmake violates the policy CMP0004.

Symptoms:
CMake Error at CMakeLists.txt:10 (add_executable):
Target "my_app" links to item "C:/Program Files " which has leading
or trailing whitespace. This is now an error according to policy CMP0004.

This problem occurs when building on Windows when we depend on libraries located (for example) in "C:\Program Files (x86)..."
Merge pull request #1151 from jet47:gpubgsegm-refactoring
Merge pull request #1221 from philippefoubert:branch_cmake_cmp0004
Merge pull request #1079 from AlexeySpizhevoy:master