Added the defaultNorm() method to the DescriptorExtractor class. This method returns the default norm type for each descriptor type. The tests and C/C++ samples were updated to get the norm type directly from the DescriptorExtractor inherited classes.

This was reported in feature report #2182 (http://code.opencv.org/issues/2182). It will make it possible to get the norm type usually applied matching method for each descriptor, instead of passing it manually.

Also fixed some typos and code alignment
Also adapted tutorial CPP samples
Fixed some identation problems

If we have perfect matches (min_dist == 0.0), then strict comparison
fails. Making it non-strict results in treating perfect matches as
good.

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

These codes should be included into regular builds.

Changes made for OpenCV 2.4.2 compatibility

Added tutorial for features2d using homography to find a planar object (Based on the well known find_obj.cpp