[request] Suggesting a list of minor changes

Hi! I have a few suggestions that has been implemented in my forked repo:

• Since there is no timer even though there is a --print-time-info option, I added a timer using cudaEventElapsedTime to measure the GPU runtime, both in main.cpp and match.cpp. I can also add the timer for the CPU side on loading the images, writing data to a file, etc.
• I am running the code on a server which does not have a DevIL support and I do not have the authority to the root access. Thus, I added OpenCV support that reads the input image. This is optional: if there is no OpenCV, then it falls back to the current implementation.
• Feature orientations are written to the file output-features.txt instead of 0 which is currently a placeholder.
• The feature matching results are transferred from the GPU memory to the CPU memory so that they can be written to a file.
• The README file is updated to include how a new user can do a quick try. Honestly I spent some time trying to figure out where the execution files are, what command should I give, etc. A clear instruction would be very helpful.

I can open a pull request to address the above changes, but would like to hear if you have any thoughts. Thanks!

Review main.cpp and match.cpp to understand the existing timing, image-loading, and result-transfer paths, then inspect the README and output-features.txt handling. The proposed work is complete when runtime information, optional OpenCV loading, feature orientations, CPU-visible matching results, and quick-start instructions are all addressed.