main: Close runDialog as necessary on session mode changes

We already do this for looking glass, but it makes even less sense
for the normal run dialog - if a mode sets runDialog to false, the
intention is to not allow executing aribitrary commands.

https://bugzilla.gnome.org/show_bug.cgi?id=708218
keyring: Port to ClutterTableLayout

We don't make use of any functionality StTable provides over
ClutterTableLayout, so port all users to the Clutter layout
in order to remove our own copy of the code.

https://bugzilla.gnome.org/show_bug.cgi?id=703833
networkAgent: Port to ClutterTableLayout

We don't make use of any functionality StTable provides over
ClutterTableLayout, so port all users to the Clutter layout
in order to remove our own copy of the code.

https://bugzilla.gnome.org/show_bug.cgi?id=703833
keyring: Don't allow ellipsization of Password label

We don't want the password entry to grow when entering more characters
that fit the available width; as labels' ClutterText ellipsizes by
default, the password label allows the entry to grow by shrinking.
Setting the appropriate ellipsize mode fixes this.

https://bugzilla.gnome.org/show_bug.cgi?id=708324
networkAgent: Don't allow ellipsization of Password label

We don't want password entries to grow when entering more characters
that fit the available width; as labels' ClutterText ellipsizes by
default, the password labels allow entries to grow by shrinking.
Setting the appropriate ellipsize mode fixes this.

https://bugzilla.gnome.org/show_bug.cgi?id=708324