Wait for interactive thread to finish clean up

[AshlinHarris]

I have not found a simple way to make the main thread wait for the timer to finish. As a result, the final cleanup step has been running after the REPL prints a new line, so the final frame isn't cleared.

Can anything like fetch or wait from Distributed.jl be made to work here? Otherwise, the signaling mechanism might have to be modified to allow reply signals from the interactive thread.

[AshlinHarris]

For now, I've just added sleep(0.5) in the macro after the close signal is sent.

[AshlinHarris]

The docs say wait or fetch should work. I'll experiment some more with the timer and spinner status.

[AshlinHarris]

The functiontimer_spin needs to wait until the timer is closed before returning, but I believe wait(Timer()) just wakes up the thread everytime the Timer elapses.

[AshlinHarris]

The next PR should fix this issue. Instead of waiting for the timer to be closed, timer_spin just waits until the spinner status is closed.

Additionally, I removed the const designation from the signaling function, since this caused issues with repeated calls.