Enum reform

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Add variant type and a few convenience functions

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Rename MessageItems to MessageItem, and add dict support

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Add client support for org.freedesktop.DBus.Properties

Signed-off-by: David Henningsson <david.henningsson@canonical.com>