Queue testing

In the app-framework package, an executable called queue_IO_check exists which writes and reads integers to instances of classes which implement the app-framework's Queue interface class. It can be run without arguments, in which case the default is for one thread to be writing integers spaced apart in time by an average of 5 milliseconds and another thread to be reading them spaced apart in time by an average of 5 milliseconds. However, you can also control the number of threads doing the writing and/or reading, as well as how full the buffer is at the start of the program; to see all the options and their defaults, run buffer_IO_check --help. Note that to see messages announcing individual pushes and pops, you need to turn on TRACE's debug level.