Re-writing javadoc for Sense. Get application context.

Start to rewrite javadoc for Sense. Now Sense is holding the applicaiton
context instead of activity application passed to init.
Avoid exception when stop is called twice.
Terminating specific service if not specified by services.

In init functions for Sense, terminate specific service if not
specified by services argument.
Use LinkedList for storing listeners.

Now sensor services use LinkedList for storing listeners.
Add debug output for Sense.
Merge branch 'feature/sense-fix' into develop