Concurrency/cuda stream Improvements

[ptheywood]

Additional use of concurrency / improvments implemented during the cineca hackathon

• Async/streamed id generation related functions (for birth)
• Message output post processing
• Agent birth post processing
• Agent death post processing
• Batched memcpy
• Pinned memory.
• Stream ownership / access.

[ptheywood]

A decent chunk of the todo's in this have been covered by @Robadob since this was made, however there are still uses of non-async default stream cudaMemcpy in getDeviceNextID, so I won't close this yet (but won't resume working on this as a priority either)