Fix some bugs and some other coding issues found using pylint

The user may define parameters needed by the os_type classes to perform
the system preparation tasks.

A new needed_sysprep_params method is added to os_type.OSBase that
returns a list with parameters that should be defined by the user.

python-dialog package in OpenSUSE decorated the returned enabled
choices from a dialog checklist with `"'. Remove those characters

The system preparation tasks could be printed multiple times in the
help dialog.

In the documentation and the printed messages, remove all references
to ~okeanos, pithos or cyclades.

When registring an image, use the information returned by the
kamaki register method to construct the metadata file.

When dumping the image to the local filesystem, store the image
properties and the disk-format info in the metadata file.

 * Change the authentication everywhere to use clouds
   (authentication URL and token pairs)
 * Add menu entries to manage clouds
 * Add an extra -a option in snf-image-creator to allow the user to
   specify authentication URLs

 * Prefix all private methods with _
 * Write missing docstrings
 * Move all public methods above the private ones
 * Add module docstrings where missing
 * Define source code encodings on all modules

If the image gets registered as public allow anyone to read the
metadata and the md5sum file.

Before uploading to pithos, check if any remote file gets
overwritten.

Syspreps that have already been executed shouldn't get returned by
list_syspreps

Check if the filesystem is mounted read-write before you execute
the do_sysprep function

Rename DiskDevice class to Image and move it to a seperate module.
Also, don't let the user access the os_type/* modules directly. In
Image class create the `os' member variable that will host an
appropriate instance of one of the OSBase classes.

Display the online documentation url

Support images that can only be deployed by the user that registers
the image to cyclades

You don't need the account name. You can fetch it from astakos using
the authentication token.

Latest versions of synnefo require user id instead of e-mail to
authenticate.

Create a new dialog_menu module to host all the "expert mode" code.
Check the code with a new version of pep8

Fix various typos in messages, add .gitignore file for
automatically produced intermediate files.

Every time you tried to reupload an image, the dialog displayed the
pithos url instead of the image filename as initial value.

The account info was saved in the token field in .kamakirc

Fix some typos and overwrite the yes/no labels of the wizard/expert
mode yesno dialog

Also move it to a separate module.

Logging can be enabled using the -l input option

A user can now create and upload an image using the wizard

The system does not perform anything yet when in wizard mode.

Create the new python module to host the aforementioned code.

If present in the kamaki configuration file, the user will read
the ~okeanos credentials using the kamaki config interface.
Whenever the user changes the ~okeanos credentians, the changes are
pushed back to kamaki.

Not fully implemented yet