debugger: Use a JSON-like notation for printing a variable's structure.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
debugger: Less noise when printing all available variables in the prompt.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>
Merge: Debugger clean

Simple cosmetic changes to the debugger, clearer, less verbose when executing several commands.

Pull-Request: #478
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>