Convert to Logging System

[LucasYoung]

Throughout PNav.cpp and CV.cpp messages are outputted using std::cerr.

These messages should use the logging system by providing the message and its appropriate logging level to a Log object.

A Log object is passed to both the PNav and CV threads. Here is the function prototype of the PNav thread and CV threads respectively:

void PNavLoop(configContainer *configs, Log &logger)
void frameLoop(unsigned int &nCaptures, configContainer *configs, Log &logger)

Use this Log object to output log messages. You may have to pass this object to the thread's helper functions if necessary.