Feature/frame buffer mode

[Fixstars-momoko]

Added the param to U3V class that switch buffering frames to queue or discard them.

When frame_buffer_modeis true

• frames are queued up to max buffer_size (currently 1GiB)

When frame_buffer_modeis false

• Check all streams' output buffer size
• Find max N for all i where N < the number of output buffer size of stream i
• Discard N-1frames from queue

[Fixstars-momoko]

updates:

• changed the name of the parameter frame_buffer_mode to realtime_diaplay_mode where frame_buffer_mode == true is equal to realtime_diaplay_mode == false.
• updated u3v camera example code to sat realtime_diaplay_mode = true as a default for both c++ and python.