expanded the CV_Assert in pyrdown_ to check for empty mats
Merge pull request #1208 from berak:Bug_3094
Added the sample from patch #2288 : reading in sequence of images

Added bugfixes
- Changed CV_WINDOW_NORMAL to 1
- Changed the help function to static
- Added extra help information on mask specifics
Merge pull request #1166 from StevenPuttemans:patch_2288
Merge branch 'master' of https://github.com/Itseez/opencv.git