modified HoughCircleDemo to introduce variable params via trackbars

Conflicts:
	samples/cpp/tutorial_code/ImgTrans/HoughCircle_Demo.cpp
improved error handling
fix typos
fix indent
Remove all using directives for STL namespace and members

Made all STL usages explicit to be able automatically find all usages of
particular class or function.

(cherry picked from commit 2a6fb2867e2fc639e0675eed8abb1688de4539ec)
(only cherry picked "apps/trancascade")
Fixed compilation errors: removed using namespace from hpp file. This led to pulling cv::ACCESS_MASK to global namespace where conflict with the same name in 'windows.h'

Conflicts:
	apps/traincascade/boost.cpp
build fix
fix exception being thrown when no arguments are passed
fixed perf tests for bgfg segmentation
disabled MOG2 performance test (sanity check fails on CUDA 6.0)
Merge pull request #1873 from abak:hough_24
Merge pull request #1879 from LeszekSwirski:traincascade-2.4
Merge pull request #1885 from jet47:gpu-bgfg-test-fix