See feature 2862

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.

ReST directive was used. Also fixed some other ReST directives that were
not correct and removed some warnings during buildbot checks.

- Used lunix style slashes - works on most systems
- Removed all trailing whitespaces

Previously it was missing.
Ordered all descriptors by year of first publication.

only file:  common_interfaces_of_descriptor_matchers.rst

Invalid links and refences fixed.
SpaeseMat class documentation updated.

All errors were found by doc/check_docs2.py

Documentation: fixed class/struc members documentation; added warning on incorrectly documented member