auto-move-windows: Move check for dynamic workspaces

Move the check into checkWorkspaces rather than replacing the function
conditionally, to handle changes to the setting.

https://bugzilla.gnome.org/show_bug.cgi?id=728865
auto-move-windows: Respect keep-alive flag in checkWorkspaces

https://bugzilla.gnome.org/show_bug.cgi?id=728865
auto-move-windows: Take workspaces in startup sequences into account

See https://bugzilla.gnome.org/show_bug.cgi?id=664202 for the
corresponding patch in core shell.

https://bugzilla.gnome.org/show_bug.cgi?id=728865
auto-move-windows: Never show the overview after removing workspace

This follows the core shell behavior, where we stopped doing this
a while ago.

https://bugzilla.gnome.org/show_bug.cgi?id=728865
auto-move-windows: Never remove the active workspace

Follow core shell in never removing the active workspace.

https://bugzilla.gnome.org/show_bug.cgi?id=728865