Add a result() method in the output interface

By default the output goes to sys.stdout. This is used in snf-mkimage
to output the plankton answer when registering an image to a synnefo
deployment.

This resolves #21
Remove cleanup_password sysprep from freebsd.py

bsd.py already contains it.
Add Info menu entry in the Image Registration Menu

This displays the registration info as returned by ./kamaki and gives
the user the option to save it in a file.
Beautify the meta file content

Add indent=4 in the json dump execution