Fix ConcurrentModificationException in SubscriptionContext
Merge pull request #1049 from aledsage/fix/ConcurrentModificationException

Fix ConcurrentModificationException in SubscriptionContext
Remove code deprecated since 0.4.0
Further changes from deprecation

- Mostly changes required due to removal of methods in Task subsystem
- Fixing Groovy deprecated uses (not found during IDE refactor)
- Also removed a method deprecated in 0.5.0
additional tidies for #1053 (removing deprecated code around tasks and jmx)
include --batch-mode for archetype example