Correction of the basic stitching process (using high level
functionality of OpenCV bad performance but functional) :
- Folder and snapshots path are now pass through arguments of JNI
function.

TODO : See stitching pipeline on OpenCV docs with stitching_detailed.cpp
sample in order to accelerate things.
It seems that stitching pipeline needs the entire set of pictures in
order to calculate SIFT matrix. (Read abstract Automatic Panoramic Image
Stitching using Invariant Features (ijcv2007.pdf => Google))