Common/Makefile
* Added dependency from Boost IOstreams library, used to read zipped
file streams.

Common/include/FileUtils.hpp
* Declared functions to save/load descriptors to binary format using STL
functions, to load an specific descriptors row from binary format, and a
function to load descriptors matrix statistics without loading and
parsing the complete file.

Common/src/DynamicMat.cpp
* Loading descriptors matrix statistics using newly implemented function
in FileUtils namespace.

Common/src/FileUtils.cpp
* Defined functions declared in FileUtils header.

Common/tests/IODescriptors_test.cpp
* Implemented tests for the new functions in FileUtils namespace except
for the one to compute OpenCV matrix statistics (row, col, type).

Common/tests/.gitignore
* Ignored files produced as part of the tests execution.

VocabLib/tests/VocabDB_test.cpp
* Added extension to the file where nn index is saved.

VocabLib/tests/.gitignore
* Ignored files produced as part of the tests execution.