FEATURE: added grunt multi-task 'mozilla-cfx'

- bumped npm version to 0.2.0dev
- defined mozilla-cfx grunt multi-task to be able to run cfx using custom
  arguments
- renamed utility scripts to cfx.sh and cfx.bat
- show cfx output on debug mode (e.g. grunt mozilla-addon-sdk:xpi --debug)
- minor tweaks on error handlings