KMajorityLib/include/CentersChooser.h
* Added elements type to the template so that data can be casted before
using distance object.

KMajorityLib/src/KMajorityIndex.cpp
* Refactor due to change in CentersChooser class.

VocabBuildDB/VocabBuildDB.cpp
VocabLearn/VocabLearn.cpp
VocabMatch/VocabMatch.cpp
* Parametrized descriptor type to instantiate vocabulary tree with the
proper template types.

VocabLib/include/VocabTree.h
* Created base class for vocabulary tree to instantiate class with
different template parameters.
* In method computeNodeStatistics, implemented code for computing
centroids in case descriptors are real valued.
* In method computeClustering, refactor due to change in CentersChooser
class, casted input data to the distance object, implemented code for
computing centroids in case descriptors are real valued.
* In method quantize, casted input data to the distance object.
* In methods addImageToDatabase and scoreQuery, changed validation rules
so that non binary descriptors are allowed.