changed to 4-space indentation to match rospy style guide. Fixed bad indentation that had a 'else' as the alternative to an 'for'
an action server's start() command needs to come after all variable used by its callback are initialized
Renaming the lock to match the variable that it protects, started cleaning up the mutex logic. (

* you can't do self.lock.acquire() within a "with self.lock" statement!
* pulling statements out of the lock statement that don't need to be protected
* ... I think there's still some refactoring that needs to happen wrt the locks
Whoops! removing errant semicolon.
removing obvious comments; making point_list local rather than member variable, since only one function uses it, and it's re-initialized every call
pulling more unnecessary member variables into local variables
More code cleanup.

* turned more class vars into local vars
* tightened scope of "with self.lock:" blocks
* all time used is now that of the published sensor message, rather than whatever the current time is
more minor cleanup