Massive cleanups to applications for LOCAL_USER handling and some other things.

In general, LOCAL_USER_ADD/REMOVE should be the first/last thing called in an
application.  An exception is if there is some *fast* setup code that might
halt the execution of the application, such as checking to see if an argument
exists.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6832 65c4cc65-6c06-0410-ace0-fbb531ad65f3