SPNV 0.2.0

• Ported the window/graphics code to SFML 3
• Added the possibility to switch between all panorama pictures in the same directory
• Added a command line option for starting in fullscreen mode
• Increased performance by adding OpenMP parallelization
• Reduced CPU load while dragging but not actually moving the cursor
• Cleaned up and improved CMakeLists.txt, removed the library target
• Fixed display projection boundary checks and wraparound
• Fixed left/right margins (now black) when horizontal FOV is smaller than window width
• Added a Cppcheck script
• Made a few other, minor improvements