Unify booleans coming and going from dbus

I think we should take another look at using dbus Variants, and making the dictionaries we use as DBus parameters be of type (string, variant), instead of (string, string).

On the upsides, we won't have the problem mentioned on this bug, we might be able to send a DBus.dictionary as a value, it will look cleaner.

On the downside, in python-dbus, using variants is more noisy than just strings. For instance, to build up the dict to send thru dbus, each value should be created as dbus.String(u'abc', variant_level=1).

For now we'll follow up syncdaemon's Dbus API convention that is:

'' for False
'True' for True (or any other string that returns True for bool())

This bug was fixed in the package ubuntuone-control-panel - 0.1.0-0ubuntu1

---------------
ubuntuone-control-panel (0.1.0-0ubuntu1) natty; urgency=low

  * debian/control
    - depends on ubutuone-client >= 1.5.1
    - depends on ubuntu-sso-client >= 1.1.7

  * New upstream release.

    [ Natalia B. Bidart <email address hidden> ]

      * Updated list of messages to be shown on the overview panel (LP:
      #690379).

      * Implemented callback for failure when loading devices.

      * Added a spinner on every UbuntuOneBin to be shown while loading the
      panel content.

      * Devices can now be removed (LP: #691295).

      * Migrated dbus_client to use non-deprectaed SSO D-Bus API.

      * Added clear_credentials to dbus_client module.

      * Implemented devices tab (LP: #690649).

      * Maximum size is set using geometry hints (LP: #683164).

      * Added logging to dbus_service and backend.

      * Error signals now sent the object id when available (LP: #691292).

      * After machine was added, Folders page is shown (LP: #674459).

      * VolumesInfoError signal is now handled (LP: #690292).

      * When FileSyncStatusError is received, no more DbusException messages
      are leaked to the end user (LP: #690305).

      * User can now subcribe and unsubscribe from folders (LP: #689646).

      * Dbus booleans are now those strings whose bool() defines its value. So,
      '' for False and any other non empty string for True (LP: #683619).

      * File sync status is retrieved and displayed in the right top corner
      (LP: #673670).

      * Adding handling for file sync disabled (only backend for now).

      * Management panel is not twined itself if CredentialsFound signal is
     received several times (LP: #683649).

    [ Rodney Dawes <email address hidden> ]

      * Default to None and initialize if None in code, instead of mutable
      defaults.
 -- Natalia Bidart (nessita) <email address hidden> Wed, 22 Dec 2010 11:15:04 -0300