Investigate using co-routines for lower level concurrency

[sureshjoshi]

Using Dispatchito is neat, and has a lot of functionality, but there is also a lot of cruft and it's not easy to test.

Need to examine if there is an easy port to co-routines to reduce the amount of code. Having a synchronous API would make a lot of handshaking easier, and there could still be a queue API.

Alternatively, could use a co-routine extension, like there is an Rx extension.