Added a check for project tree refresh to only execute on OSX.
Added a check to only activate the Output window if it's not activated.

This reduces flicker by redrawing the project tree only when needed.
Improved handling of upvalues with __tostring method in the Stack window.
Added centering of current line during debugging.
Fixed a static analyzer issue with anonymous functions defined in expressions (fixes #3).
Enabled full debugging for Corona on OSX.
Fixed debugger output not being suppressed on Linux and using wlua.