Bug 817543 slow toolbox

* lazy load Tilt: let's not load all the Tilt JSM at startup.
* avoid flickering: toolbox visibility to collapse until it's ready.
* cat Cmd* > BuiltinCommands.jsm: nothing to see here (no code change).
* removed Cmd*.jsm: these files are not useful anymore.
* Reduce Commands.jsm: the goal of this work. Less JSMs.
* Cleaning new BuiltinCommands.jsm file: compiling all the Cmd* file into one sensible file.
* gcli update: Joe's code.