Use unique identifier as reference for asynchronous service execution.

git-svn-id: http://svn.zoo-project.org/svn/trunk@514 4b6b6ad6-68b3-4dcc-9231-bd9b83bc5dc3
Use the _getStatus function to use unique identifier and free the allocated memory.

git-svn-id: http://svn.zoo-project.org/svn/trunk@515 4b6b6ad6-68b3-4dcc-9231-bd9b83bc5dc3
Call exit from the child processes and make sure to remove zombies from process list.

git-svn-id: http://svn.zoo-project.org/svn/trunk@516 4b6b6ad6-68b3-4dcc-9231-bd9b83bc5dc3
Update ZOO-Client API and add its jsdoc documentation. 

git-svn-id: http://svn.zoo-project.org/svn/trunk@517 4b6b6ad6-68b3-4dcc-9231-bd9b83bc5dc3