Multi-Frequency Threads

[synthfi]

Currently threads have to be scheduled at the same rate. Need to be able to schedule threads at multiple rates, to help support simulation of what software will run like on hardware.

Implementation for NRTScheduler:

• add in new positive integers parameter
• dictates number of times to run all models before calling to the barrier wait
• if soft real time is enabled, add wait time at the end of the frame to wait to the start of the next frame
• uses mutexes? to ensure that threads that align can