Put wizard in a modal dialog

With some UI transitions removed during the port away from clutter, its
better to have it in a dialog. This also helps reduce the size of wizard
to buttons on both sides are not so far away from each other and hence
easy to reach.

Known issue: Wizard dialog changes size for some reason when arriving to
review page.

https://bugzilla.gnome.org/show_bug.cgi?id=733367
Drop now redundant WizardToolbar

https://bugzilla.gnome.org/show_bug.cgi?id=733367
wizard: Remove now redundant cancel_button field

https://bugzilla.gnome.org/show_bug.cgi?id=733367
wizard: Make review page fit in smaller space

One of the points of putting the wizard into a dialog is that it would
then take less screen space. Without these adjustments, wizard takes a
lot of horizontal space.
Drop WizardSidebar

Drop the sidebar from wizard. It looks weird now in the dialog and what
little functionality it provides will be replaced in the following patch
through dialog title.
wizard: Specify step number in title
Put properties in a modal dialog

With some UI transitions removed during the port away from clutter, its
better to have it in a dialog.

Known issues:

* This implies that now we can't change name of machine through title
  anymore. Main reason is that there seems to be no way to set a custom
  widget as title of a dialog but I don't think many will miss this
  feature anyway, especially now that its a dialog.

* Page titles are missing in the sidebar when coming to properties from
  wizard and hence the ability to switch pages.

https://bugzilla.gnome.org/show_bug.cgi?id=733367
Drop now redundant PropertiesToolbar

https://bugzilla.gnome.org/show_bug.cgi?id=733367
Drop now redundant Sidebar class

https://bugzilla.gnome.org/show_bug.cgi?id=733367
mini-graph: Adjust for bigger size

We are about to put mini graphs into properties' main view (and then
remove them from sidebar), where they'll need to be much bigger than
they currently are.

TODO: Make them look good on bigger size as well.
i-properties-provider: Add Property.flushed signal

Add a signal to Property to notify interested parties that said property
has been flushed.
libvirt-machine-props: Add resource stats graphs

Add resource stats graphs to properties under 'System' page.

This is part of move of sidebar contents to main view before sidebar can
be dropped.