Improved usability with instructions and examples

[6o6o]

Hi. Thanks for porting the software for CMake and simplifying the building process. Unfortunately, the demo app is lacking basic functionality and may have poor usability for an average user without a PhD in math. After some experiments I try to make it more accessible and hopefully useful for general public without major modifications to the library. Here are some of the key changes:

• Greater flexibility with command line arguments
• Consecutive processing of multiple images or video frames
• Dynamic step size adjustment depending on distance to the camera
• Bugfixes when loading the model and reading .obj file with extended formats
• Examples and instructions are provided