fixed bug in opencv_stitching (corrected resize images step), added matches checking (both 1->2 and 2->1 must be presented)

a lot of small corrections to bring down the number of undocumented functions, reported by the script; added em.cpp sample

a lot of small corrections to bring down the number of undocumented functions, reported by the script; added em.cpp sample

improved convertPointsHomogeneous documentation. added convertPointsTo/FromHomogeneous (ticket #1011)