Restructured code to remove multiply-nested if conditions.
Added a thread, but ST2 freezes soon after displaying lookup results.
Moved bulk of cscope-related code to a worker class that extends threading.Thread while ensuring that all ST2-related calls happen only from one function that will execute in the main thread.
Display status message while fetching results and an error message if cscope database couldn't be found.
Added an activity indicator to the status bar similar to the one used by PackageControl