Update SYNQueueTask initializers
Update SYNQueueTask initializers

- Made full initializer private
- Added sensible convenience initializer
- Noted compatibility issue with objc-c when using convenience
initializers

Syntertainment/SYNQueue,THREDOpenSource/SYNQueue,Syntertainment/SYNQueue,THREDOpenSource/SYNQueue,RajaveluC/SYNQueue,RajaveluC/SYNQueue