Bug 984365 - Refactor and split out BuiltinCommands.jsm; r=mratcliffe,robcee,panos

BuiltinCommands.jsm was huge to avoid slowing things down by having many
modules loading.

To avoid splitting it up from slowing things down we want to delay loading
commands. Create [add|remove]ItemsByModule to allow us to lazily add modules,
and convert all command modules to use this.

Then break up BuiltinCommands into a set of files, for each command, and do
some refactoring to use JS files rather than JSMs and use "use strict".

--HG--
rename : browser/devtools/commandline/Commands.jsm => browser/devtools/commandline/commands-index.js
rename : browser/devtools/debugger/CmdDebugger.jsm => browser/devtools/debugger/debugger-commands.js
rename : browser/devtools/inspector/CmdInspect.jsm => browser/devtools/inspector/inspector-commands.js
rename : browser/devtools/responsivedesign/CmdResize.jsm => browser/devtools/responsivedesign/resize-commands.js
rename : browser/devtools/scratchpad/CmdScratchpad.jsm => browser/devtools/scratchpad/scratchpad-commands.js
rename : browser/devtools/styleeditor/CmdEdit.jsm => browser/devtools/styleeditor/styleeditor-commands.js
rename : browser/devtools/tilt/CmdTilt.jsm => browser/devtools/tilt/tilt-commands.js
Bug 983712 - Fix the GCLI menu to remove scrollbars; r=mratcliffe