Merge pull request #31 from abaxter-rh4u/master

Added null handling to AsyncCommandExecutorBean
Merge pull request #32 from abaxter-rh4u/master

Add guard against null release id when we need it
Merge pull request #33 from abaxter-rh4u/master

Added task impl classes to client
Merge pull request #34 from abaxter-rh4u/master

Split out AsyncCommandExecutor interfaces into client artifact