Fixed OS X compilation error in window_cocoa.mm

Un-commented `NSApplicationActivationPolicyRegular` argument (in leu of zero) and got rid of problematic dereference
Documentation fix on py_tutorials/py_feature2d
updated linux installation documentation
Merge pull request #3422 from avdmitry:install_doc_update
Merge pull request #3424 from dsjolie:daniel
Typos in CMake
Merge pull request #3431 from PhilLab:patch-3
silence cmake 3.0+ warnings on LOCATION attribute
Add cv::setWindowTitle to highgui
Merge pull request #3432 from taka-no-me:wintitle
Merge pull request #3411 from eltermann:master
Merge pull request #3409 from fish2000:patch-1