datasets loading module

Module for loading datasets for Fall2014 OpenCV Challenge.

I hightly unsure about files structure, because I worked on separate application and just converted it to module today (we need hurry as Challenge should start September, 1).

Document in doc/ is very first version and will be updated.

src/ & include/ contain main code.
samples/ - samples how to work with this code.

tinyxml2/ - 3rd party library, in my project structure was in 3rdparty/ folder, but this didn't work after converting to module.

I only checked that module was successfully built.
sure, my current idea is to implement hierarchy for each object in train\test vectors. In this case these vectors could be moved in base class and all work with them will be possible through base interface. The only inconvenience in this case is that user will need to cast concrete object before start work with it.