props-toolbar: Only return to collection if prev state was display

In commit commit b68642b we started to always return to 'collection' UI
state on user clicking back button if VM is not running. This was to fix
an issue that is specific to display->properties->display transition and
it breaks for wizard->properties->wizard transition. Lets fix the latter
by making sure we only return to collection state if previous UI state
was 'display'.

https://bugzilla.gnome.org/show_bug.cgi?id=738851
snapshot-list-row: Start machine on revert if prev state was DISPLAY

Its wrong to always override the state of the machine to running after
reverting to a snapshot. This was only done for the case of user
entering snapshots view from display so lets ensure that indeed is the
case before overriding the state of machine.

With this change, libvirt should ensure that after getting reverted to a
snapshot, machine is back in the state that it was when the snapshot in
question was taken.

https://bugzilla.gnome.org/show_bug.cgi?id=735688
snapshots-list-row: Always display msg when reverting

We were not displaying "Reverting to SNAPSHOT_NAME" message and spinner
if machine was not in running state. The rationale was that in
non-running state, reverting is a very quick operation and therefore the
stack page switch animation looked weird.

However reverting is not always very fast in this case and the missing
indication is a bit of a UX failure when that happens. Moreover, the
quick page switch doesn't look that weird after all. If we decide to
still address the latter, we can always introduce a very short artificial
delay.
machine: Make 'can-save' a virtual property

Instead of subclasses overriding the value of 'can-save' property,
let them override the property getter itself so they can implement
smarter (more dynamic) getters for it.

https://bugzilla.gnome.org/show_bug.cgi?id=730793
libvirt-machine: Smarter 'can-save' implementation

This property shoudl check the state of the machine rather than its user
having to do that in addition to checking the value of this property.

https://bugzilla.gnome.org/show_bug.cgi?id=730793
libvirt-machine: Add private 'saving' boolean field

This field is set to true if machine is being saved currently.

https://bugzilla.gnome.org/show_bug.cgi?id=730793
libvirt-machine: Not savable when being saved already

Don't claim the machine to be savable if its being saved.

This solves the issue of pause button still being available to user and
Boxes leading into interesting scenerios if user clicks on the button.

https://bugzilla.gnome.org/show_bug.cgi?id=730793
libvirt-machine-props: Ensure name change is saved

The two different UI components (name property and toolbar title) that
can be used to change the name of machine were using two different
methods to do so and hence changing the name from toolbar title wasn't
getting the name change saved.

This patch unifies the method to change the name and ensures that change
of name is saved.

https://bugzilla.gnome.org/show_bug.cgi?id=736096
wizard-source: Activate on URL entry activation

Proxy over the URL entry activation so that wizard continues to the next
step if user hits 'Enter' key after typing URL.

https://bugzilla.gnome.org/show_bug.cgi?id=733975
downloader,HTTP: Ignore all chunks until redirected

In case of HTTP redirection, first chunks we get are of the HTML
document we recieve from the original URL we tried to download. Lets
ignore those bytes and only save the chunks of the target resource.

https://bugzilla.gnome.org/show_bug.cgi?id=738168
vnc-display: Correct arguments to a signal handler

Correct arguments to handler of Vnc.Display.vnc_auth_credential signal.

https://bugzilla.gnome.org/show_bug.cgi?id=736099
vnc-display: Correctly cast to DisplayCredential

DisplayCredential is not a class so you can't use 'as' operator to cast
to this type.

This together with previous patch, fixes a crash that always happens if
you try to connect to a VNC box that has password on it.

https://bugzilla.gnome.org/show_bug.cgi?id=736099
NEWS: Correct minor mistakes in last release entry
NEWS: Release 3.14.1.2