a new version of gtdebugger

A new version of GTDebugger was just integrated. Several issues were addressed. Some more notable things are:

- the stack shows columns for class, method, other info

- there are new keybindings in place that do not collide with the text editor

- the accept/cancel buttons are in the contextual menu at least for Pharo 5

- the variables pane received a label

There are still some things todos left like:

- the columns in the stack should be resizable

- thisContext, stackTop

- perhaps make the key bindings controllable through settings

We kindly invite everyone to test it and provide feedback.

Cheers,

Doru